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LRS Micro-g LaCoste FG5 Manual Download Page 147

Index

 

 

 

Laser Light

 

Path...................................................................... 2-2 

LED

......................................................

2-4

, 2-12, 2-18 

Infrared ..................................................... 2-12, 2-19 

LED Driver ........................................................... 4-30 

Leveling

 

Dropping Chamber (setup) .................................. 3-8 
Superspring........................................................ 3-11 

Limit Switches

 

Adjustment ........................................................ 4-18 

Linear Actuator ..................................................... 2-19 

Linear Bearings

 

Lubrication .......................................................... 4-6 
Micro-g Modifications......................................... 4-6 
Replacement ........................................................ 4-6 

Linear Detector ..............................................2-4, 2-18 

Lower Reference Height

 

Measuring............................................................ 3-5 

Lubrication

 

Linear Bearings ................................................... 4-6 
O-Ring................................................................. 4-4 
Pulley Bearings.................................................... 4-8 

M

 

Mach-Zender Interferometer ................................. 2-10 

Maintenance

 

Annual ............................................................... 4-32 
Semi-annual....................................................... 4-32 

Maintenance Schedule .......................................... 4-32 
Measuring Lower Reference Height ....................... 3-5 
Measuring Upper Reference Height........................ 3-9 

Micro-Switches

 

Adjustment ........................................................ 4-18 

Mirror #4

...............................................................

2-9

 

Model AL-1 Laser

 

Setup.................................................................... 3-2 

Modes

 

Dropper Control................................................. 4-25 

Motor Driver Circuit ............................................. 4-31 

O

 

OLIVIA...............................................2-15, 2-16, 3-16 
Optical Glass Sphere............................................... 2-4 

Optics

 

Function............................................................... 2-9 

Optimizing Fringes

.............................................

3-14

 

Oscilloscope Settings......................................... 3-15 

Optional Hardware

.............................................

2-15

 

Environmental Sensors Package........................ 2-15 
Rotation Monitor ............................................... 2-15 

Optional Systems .................................................. 2-20 

O-Ring

 

Lubrication .......................................................... 4-4 

O-Rings

 

Inspection ............................................................ 4-2 
Lubrication .......................................................... 4-2 

P

 

Packing

 

Dropping Chamber.............................................3-21 
Dropping Chamber Tripod.................................3-21 
Electronics .........................................................3-19 
FG5 ....................................................................3-19 
Interferometer ....................................................3-21 
Rotation Monitor................................................3-20 
Superspring ........................................................3-22 
System Controller ..............................................3-20 
Turbo Pump .......................................................3-22 

Photo Detector.......................................................2-19 

Position

 

Cart ....................................................................4-27 

Power

 

Shutting Off .......................................................3-18 

Power Mains Module ............................................2-20 

Power Supplies

 

Function .............................................................2-20 

Power

 

Supply

 

APD ...................................................................4-21 

Pressure Sensor......................................................2-20 

Program

 

Setup ..................................................................3-17 

Pulley Bearings

 

Lubrication...........................................................4-8 

Pulses

 

Scale Factor .........................................................2-8 
TTL......................................................................2-8 

Pump

 

Ion........................................................................2-6 

R

 

Rattler Plate ...........................................................2-10 
Reference Beam ......................................................2-9 

Removal

 

Dropping Chamber Cover....................................4-1 
Service Ring.......................................................4-13 

Replacement

 

Coil ....................................................................4-14 
Drive Belt.............................................................4-3 
Dropping Chamber Cover....................................4-2 
Ferrofluidic Feedthrough .....................................4-4 
Flexures..............................................................4-15 
Focus-Lever Motor ............................................4-18 
Linear Bearings....................................................4-6 
Rotary Shaft Encoder...........................................4-8 
Shaft Bearings (Drive Pulley) ..............................4-7 
Shaft Bearings (Top Pulley).................................4-8 
V-Plate .................................................................4-5 

REPLAY ...............................................................2-15 

Required Hardware

.............................................

2-15

 

Hard Drive .........................................................2-15 
Memory..............................................................2-15 

Rotary Shaft Encoder

 

Replacement.........................................................4-8 

Rotation Monitor

..........................................

2-7

, 2-21 

Alignment ............................................................8-1 

 

10-3

Summary of Contents for Micro-g LaCoste FG5

Page 1: ... 2 3 1 SUPERSPRING MASS 2 12 2 3 2 SPHERE DETECTOR SYSTEM 2 12 2 4 The System Controller 2 14 2 4 1 REQUIRED HARDWARE 2 15 2 4 2 OPTIONAL HARDWARE 2 15 2 4 3 SOFTWARE 2 15 2 5 Electronics 2 15 2 5 1 TIMING SYSTEM 2 15 2 5 2 DROPPER CONTROLLER 2 17 2 5 3 SUPERSPRING CONTROLLER 2 18 2 5 4 LASER CONTROLLER 2 18 2 5 5 POWER SUPPLIES 2 19 2 5 6 OPTIONAL SYSTEMS 2 19 2 5 6 1 ENVIRONMENTAL SENSORS 2 19 2...

Page 2: ...3 20 3 4 1 ELECTRONICS 3 20 3 4 2 SYSTEM CONTROLLER 3 20 3 4 3 ROTATION MONITOR IF INCLUDED 3 21 3 4 4 DROPPING CHAMBER 3 22 3 4 5 DROPPING CHAMBER TRIPOD 3 22 3 4 6 INTERFEROMETER BASE 3 22 3 4 7 SUPERSPRING 3 23 3 4 8 TURBO PUMP IF USED 3 23 4 ADJUSTMENT AND MAINTENANCE 4 1 4 1 The Dropping Chamber 4 1 4 1 1 REPLACEMENTS AND ADJUSTMENTS 4 1 4 1 1 1 Removing The Dropping Chamber Cover 4 1 4 1 1 2...

Page 3: ...y Module 4 23 4 4 1 3 Rubidium Oscillator 4 24 4 4 2 DATA ACQUISITION 4 25 4 4 2 1 Computer Interface Cards 4 25 4 5 DROPPER CONTROLLER 4 25 4 5 1 DROPPER CONTROL MODES 4 27 4 5 1 1 STANDBY 4 27 4 5 1 1 1 To Select 4 27 4 5 1 1 2 Function 4 27 4 5 1 1 3 To Deselect 4 27 4 5 1 2 MANUAL 4 27 4 5 1 2 1 To Select 4 27 4 5 1 2 2 Function 4 27 4 5 1 3 DROP 4 27 4 5 1 3 1 To Select 4 27 4 5 1 3 2 Functio...

Page 4: ...TION MONITOR 5 13 5 3 Gravity Site Selection 5 14 5 3 1 GEOLOGIC STABILITY 5 14 5 3 2 SITE STABILITY 5 14 5 3 3 ENVIRONMENTAL NOISE 5 14 5 3 4 TEMPERATURE STABILITY 5 14 5 4 AC POWER 5 15 6 SWITCHING THE AC POWER 6 1 6 1 LASER 6 1 6 1 1 WEO Model 100 Laser 6 1 6 1 2 ML 1 Laser 6 2 6 2 Portable Ion Pump Power Supply 6 2 6 3 Computer 6 2 7 PUMPING BAKING THE CHAMBER 7 1 7 1 Choosing the Pumping Meth...

Page 5: ...nce 9 18 9 6 1 Removing Superspring Cover 9 18 9 6 2 Replacing Superspring Cover 9 18 9 6 3 Removing Superspring Service Ring 9 19 9 6 4 Replacing Superspring Coil 9 19 9 6 5 Replacing Superspring Flexures 9 20 9 6 6 Assembling Superspring 9 22 9 6 7 Replacing Superspring Focus Lever Motor 9 25 9 6 8 Adjusting Superspring Micro Switches 9 26 9 7 Packing the FG5 9 26 10 INDEX 10 1 Figure 2 1 The FG...

Page 6: ...e of Figures Figure 2 11 Timing diagram 2 16 Figure 2 12 Rotation Monitor 2 21 Figure 3 1 Superspring Interferometer Setup 3 4 Figure 4 1 Drive Pulley Assembly 4 7 Figure 4 2 Interferometer Top Lid 4 11 vi ...

Page 7: ...Table of Figures This Page is Intentionally Blank vii ...

Page 8: ......

Page 9: ...f length and time The distance scale is given by a frequency stabilized helium neon HeNe laser used in the interferometer A rubidium atomic time base provides the time scale used for the accurate timing The value of gravity obtained with the FG5 can be used without the loop reductions and drift corrections normally required when using relative instrumentation 1 2 HISTORY The FG5 is a new generatio...

Page 10: ...a stability The tripod is now built symmetrically with respect to the drop line Improvements to the electronics reflect new technology and make the instrument smaller and easier to use This absolute gravimeter is designed to work with a new rugged iodine stabilized laser system WEO model 100 traceable to the BIPM The system controller has been updated to an Intel based personal computer with a sta...

Page 11: ...rometer is used to monitor the position of the freely falling test mass The Superspring is an active long period isolation device used to provide an inertial reference for the gravity measurement The System Controller computer allows a flexible user interface controls the system acquires data analyzes data and stores the results The Electronics provides high accuracy timing necessary for the measu...

Page 12: ...mber which houses the Test Mass A Drive Mechanism is used to drop track and catch the test mass inside the drag free chamber Laser light Figure 2 1 passes through a window in the bottom of the Dropping Chamber to the corner cube inside the test mass then is reflected back down through the window to the interferometer Figure 2 2 Front view of the dropping chamber 2 2 ...

Page 13: ...Design Components and Function 2 Figure 2 3 Side view of the dropping chamber 2 3 ...

Page 14: ...tting Diode LED located on the cart directs light through an optical glass sphere attached to the test mass The sphere focuses the light onto a linear detector also mounted on the cart This system senses the position of the cart with respect to the test mass A servo motor drive belt system Figure 2 2 moves the cart inside the Dropping Chamber using active feedback from the position sensor to maint...

Page 15: ... and balanced at the optical center of the corner cube The corner cube is a three surface mirror which has the special optical property that the reflected beam is always parallel to the incident beam In addition the phase shift of the reflected beam is virtually constant with respect to any slight rotation or translation of the corner cube around its optical center1 1 Peck Edson J Opt Soc Amer 38 ...

Page 16: ...al evacuation of the vacuum system A Ferrofluidic rotary vacuum feedthrough which connects the motor shaft to the cart drive mechanism A servo motor rotary shaft encoder assembly which moves the cart and senses its position An electrical vacuum feedthrough which allows connection of the test mass tracking electronics to the controller An ion pump mounted on a 2 Conflat flange which maintains the v...

Page 17: ... top flange of the dropping chamber directly above the viewing port When the rotation monitor is not mounted a cover for the port is used to exclude ambient light from the interior of the dropping chamber during measurements 2 1 6 THE DROP In drop mode a signal from the computer to the dropper controller initiates the drop sequence The cart drag free chamber is driven slowly from its bottom positi...

Page 18: ...s s velocity Approximately a million fringes are generated during a single drop A zero crossing discriminator comparator transforms the sinusoidal fringe signals from the APD into a series of square Transistor Transistor Logic TTL pulses The pulses are scaled i e divided by a user defined factor which is set in the software typically 1000 A Time Interval Analyzer TIA measures the time interval bet...

Page 19: ...ted to achieve the best accuracy However it is more rugged than the iodine laser 2 2 2 OPTICS AND BEAM PATH Refer to Figure 2 1 and Figure 2 8 for the following description of the beam path The optical fiber directs the laser beam from the laser head to the interferometer base At the input of the interferometer a lens collimates the light from the optical fiber It is then directed to beamsplitter ...

Page 20: ...trike the detector APD and the interference fringes are converted to a Continuous Wave CW signal The CW signal is then converted to a Transistor Transistor Logic TTL signal and transmitted to the time interval analyzer The other recombined beam travels horizontally until it reaches the attenuator plate rattler This beam is split and reflects rattles between the beamsplitter coating and the uncoate...

Page 21: ...Design Components and Function 2 Figure 2 8 Side view of interferometer optics and beam path 2 11 ...

Page 22: ...cube retroreflector and an optical glass sphere 2 3 2 SPHERE DETECTOR SYSTEM The superspring sphere detector system Figure 2 10 senses motions of the superspring mass relative to the support housing An infrared light emitting diode LED located on the support housing directs light through an optical glass sphere attached to the superspring mass The sphere focuses the light onto a split photodiode d...

Page 23: ...Design Components and Function 2 Figure 2 9 The Superspring 2 13 ...

Page 24: ...using Temperature related length changes of the mainspring are compensated with an aneroid wafer assembly Figure 2 9 2 4 The System Controller The system controller is an IBM compatible PC which is used to control the gravimeter initiate drops as well as collect data distance and time for computing the gravity value It is also used to collect environmental and rotation monitor data if the FG5 is e...

Page 25: ...ng post processing and diagnostic testing It also allows the user to customize the data acquisition for each site including input output files printing options and session control The software also allows user input of site specific information such as site name code geodetic coordinates and elevation nominal air pressure and gravity gradient In addition the software allows the user to apply or no...

Page 26: ... the zero crossings of the sinusoidal fringes and outputs a TTL square wave version of the frequency swept fringe signal During a drop the fringe signal sweeps from DC to about 6 MHz The Rubidium Oscillator is an atomic resonance controlled oscillator or equivalent which outputs a stable sinusoidal signal of 10 MHz The Time Interval Analyzer TIA scales the fringes using a software specified scale ...

Page 27: ...less steel drive belt which is attached to the cart The motor also turns an optical shaft encoder that provides accurate information to the dropper controller on the position and velocity of the pulley Information on the relative position of the test mass to the cart during free fall is provided by a sphere detector system An LED and a linear detector are mounted on opposite sides of the cart and ...

Page 28: ... An infrared LED and a photo detector are mounted opposite each other inside the mainspring support housing A sphere attached to the bottom of the mass focuses the light from the LED onto the detector which transmits the resulting signal to a sphere signal preamplifier The zero position of the sphere on the test mass can be adjusted by moving the top of the main spring with a small DC motor with a...

Page 29: ...sensors package can be added to the system by itself but if the rotation monitor is purchased the environmental sensors package must be included in the system 2 5 6 1 ENVIRONMENTAL SENSORS The Environmental Sensors Package is used to record environmental data temperature and atmospheric pressure as the system is operating Atmospheric pressure data is used to compute and apply the local barometric ...

Page 30: ...em rejects translation and is only sensitive to rotation The diode laser beam reflects off mirror 1 and the beamsplitter mirror mount 2 The beam then passes down through the dropping chamber viewing port where it reflects off a flat mirror which is mounted to the top of the test mass The return beam from the test mass mirror passes through the beamsplitter and reflects off mirror 3 The beam then p...

Page 31: ...Design Components and Function 2 Figure 2 12 Rotation Monitor 2 21 ...

Page 32: ...Design Components and Function 2 This Page is Intentionally Blank 2 22 ...

Page 33: ...L AS POSSIBLE IT IS BEST TO SET UP THE FG5 ON A CONCRETE OR HARD TILE FLOOR 3 1 1 ELECTRONICS CASE 1 Place the electronics case in a convenient location about 1 meter from the reference mark 2 Check the input voltage settings and make sure they are set to the proper AC line voltage If the instrument is not set to the correct voltage see appendix A for instructions on switching the input voltage se...

Page 34: ...C and DC power switches on rear of electronics case 8 Connect the applicable power cables to the laser and Turn on the laser power Consult the instructions below for the proper laser 3 1 1 1 Model ML 1 Laser 3 1 1 1 1 Warm Up Consult ML 1 operating manual for more details Set the MODE switch to the WARMUP position Turn on the main power switch and the key switch for the laser tube HV Set the heate...

Page 35: ...O Do not adjust any other controls Nominal control settings are Signal Monitor Section Meter Select 1F Gain 1 Time Constant 1 Temperature Control Section Body Temp Mode TEMP Temperature Control Section Meter BIAS Bias Voltage Set to 0V meter Allow the laser to warm up for at least two hours or until the temperature of the laser has stabilized before beginning observations 3 3 ...

Page 36: ...How to Set Up and Run the FG5 3 Figure 3 1 Superspring Interferometer Setup 3 4 ...

Page 37: ...od Pass the gauge rod through the hole in the center of the superspring tripod and extend it until it hits the reference mark on the floor Tighten the locking screw and measure gauge length using the scale fixture which is used to measure the upper reference height see step 37 Record this value in the system check log 12 Place the superspring on the tripod Orient the superspring so the travel lock...

Page 38: ...the three tripod legs from the dropping chamber case and attach them to the tray Tighten the legs by using the 30 cm cheater bar 19 At this point the interferometer will be used to support the dropping chamber tripod First remove the dust cap from the top of the interferometer base 20 Carefully place the dropping chamber tripod on the interferometer Orient the tripod so that the small hole is 21 C...

Page 39: ... the safety HV ground to the other banana jack on the base of the dropper Tie both cables to a tripod leg with a velcro strap 26 If the vacuum in the dropping chamber has remained intact since the previous use the ion pump alone may be sufficient to pump down the chamber The ion pump will probably start if it has been off for two hours or less Appendix B discusses the use of the turbo pump 27 Befo...

Page 40: ...erclockwise raising them until they just contact the balls It is important that there is no horizontal tension between the foot and the tripod leg because it will cause the dropping chamber to shift sideways when it is lifted It is helpful to rotate or wiggle the foot slightly while it is in contact with the nylon ball to release any horizontal tension 34 After each foot is in contact with the tri...

Page 41: ...e provided The upper reference height is the distance between the top of the interferometer base and the bottom of the dropping chamber Loosen the clamp on the scale and pass the scale up through the access hole in the dropping chamber tripod while pulling the scale slightly towards yourself the hole is located directly above fiber optic input on the interferometer base until it contacts the top o...

Page 42: ...l 4 on the patch panel g 46 For the WEO Model 100 laser Connect the BNC cable from the OUTPUT connector on the front panel of the laser controller to Channel 3 of the patch panel Make sure the meter select switch on the laser controller is set to the 1F position 47 For the Model ML 1 Laser Connect the LASER LOCK on the patch panel to the REMOTE BNC on the back of the ML 1 controller this allows th...

Page 43: ... orange Lemo connector from the power supply panel to the orange Lemo connector on the motor drive assembly Connect the APD power cable green Lemo connector from the power supply panel to the interferometer base power connector 3 1 8 THE SUPERSPRING 52 Make sure the COIL switch on the superspring controller is OFF Connect the superspring control cable yellow Lemo connector from the power supply pa...

Page 44: ... the top of the mainspring relative to the inner support structure The zero position is monitored on the front panel BNC of the superspring controller marked SPHERE OUT The position can be adjusted manually or automatically to be within about 20 mV of 0 V The rotary knob on the front panel can be set to MANUAL WINDOW AUTO or REMOTE The REMOTE setting should not be used The MANUAL setting allows th...

Page 45: ...nge in gravity usually as a result of a large latitude and or elevation change from one site to the next The zero position can be set by using the AUTO mode which moves the mass to the zero position One can also move the test mass position using the MANUAL mode Before switching to MANUAL mode first set the trim pot to move the motor in the correct direction The trim pot should be set towards UP if...

Page 46: ...ddler or the mirror below the telescope mirror 2 when the alcohol pool is in the interferometer only adjust the fiber optic mounting plate Note that both beams move with respect to the telescope crosshairs as you adjust the mirror mount screws 3 1 10 FRINGE OPTIMIZING 62 To optimize the fringe signal the test and reference beams must be made perfectly coincident and parallel The two interfering be...

Page 47: ... Run the FG5 3 65 Look in the telescope and adjust mirror 2 so the test and reference spots are overlapped Use the two knobs that are diagonally opposite of each other The two beams are now coincident and parallel 3 15 ...

Page 48: ...onstant frequency fringe signal which is useful for adjusting mirror 2 68 Maximize the fringe signal on the oscilloscope by adjusting mirror 2 69 Maximize the fringe signal on the oscilloscope by adjusting the twiddler Nominal fringe signal peak to peak is 280 360 mV Record this value in the system check log 70 Terminate OSC mode by pressing TRIG on the dropping chamber controller This brings the ...

Page 49: ...k the 1f signals with a volt meter and enter the information in to Process Setup System Laser 5 Enter the desired acquisition parameters into Process Setup Acquisition 6 Enter the desired environmental system corrections into Process Setup Control NOTE Make sure the laser is warm and the meter select switch of the WEO Model 100 laser controller is set to 1f see WEO manual After reading the 1f sign...

Page 50: ... information 3 3 Shutting Down the FG5 3 3 1 COMPUTER 1 Exit g 2 Backup the data if desired 3 Shutdown the computer 3 3 2 SUPERSPRING 3 Turn the COIL switch off 4 Engage the superspring travel lock The arrow on the lock know points down when it is locked and up when it is unlocked 5 Disconnect the cable from superspring electronics 3 18 ...

Page 51: ...2 OPTION 2 WEO Model 100 Laser 6 a Set servo control to OFF recommended but not required b Turn the key switch off The green indicator light should turn off c Turn power switch off 3 3 4 DROPPING CHAMBER 7 Press RESET on dropper controller 8 Disconnect the shaft encoder motor power and cart control cables from the dropping chamber 9 Engage the dropping chamber travel lock 3 3 5 POWER 10 Turn off a...

Page 52: ... storage movement of the FG5 is less than about 8 hours it is possible to travel the dropping chamber with the ion pump supply s internal battery backup Make sure the DC and HV switches are on and pack the ion pump controller inside the dropping chamber travel case 3 If the storage is longer term pack the ion pump supply inside of the dropping chamber travel case as above but turn off all the powe...

Page 53: ...ables from the rotation monitor detector box and electronics rack and store in the rotation monitor case 10 Remove the rotation monitor from the dropping chamber two M6x35 screws and place in the rotation monitor case 11 Close the rotation monitor case and secure all latches 12 Replace the two M6x35 screws in the dropping chamber top flange and replace the viewing port cover 13 Secure the lids to ...

Page 54: ...t it in its case If the HV and safety ground cables are still connected take care not to stress them 3 4 5 DROPPING CHAMBER TRIPOD 18 Carefully remove the tripod from the interferometer base Remove the legs from the tripod Place the legs in the dropping chamber case along with the tripod tray and feet 19 Close dropping chamber case and secure all latches 3 4 6 INTERFEROMETER BASE 20 Insert the dus...

Page 55: ...ve the superspring from the tripod and place in its shipping case Note that the bullseye level points toward the air relief valve in the case 28 Close the superspring shipping case and secure all latches 3 4 8 TURBO PUMP IF USED 29 Make sure the blank flange is in place on the turbo pump intake flange 30 Make sure all covers are in place on the flexible tube and turbo pump exhaust flange 31 Unplug...

Page 56: ......

Page 57: ...s in the field it is sufficient to wipe or flush the contaminated parts with alcohol Whenever possible vent the chamber with dry nitrogen rather than air This will reduce the pump down time after the chamber is reassembled To vent the dropping chamber remove the clamp and blank flange from the vacuum valve on the service ring Loosen the vacuum valve lock ring and slowly open the valve by rotating ...

Page 58: ...ten the screws in a star pattern to equally distribute the load on the o ring 4 1 1 2 Replacing the Dropping Chamber Cover Inspect the chamber O ring and sealing surfaces Coat the O rings with a very light film of Apiezon L grease just enough to make it shiny if necessary and re install the chamber cover and lifting handles Tighten the mounting screws in a star pattern With the chamber cover mount...

Page 59: ...Adjustment and Maintenance 4 4 3 ...

Page 60: ...or alcohol on a cotton swab Wipe the new belt with acetone or alcohol to remove any traces of oil or fingerprints Thread new belt around upper and lower pulleys and place ends over the dowel pin A wire with a small hook works well to assist in threading the belt around the lower drive pulley Replace belt clamp but do not fully tighten Tension belt while manually moving the cart up and down to allo...

Page 61: ...ible use dry nitrogen to vent the chamber Loosen the English 4 40 clamp screws on the Helical coupling between the motor and the Ferrofluidic vacuum feedthrough by reaching through the access hole in the motor mount Remove the three 28 English screws which attach the motor mount to the Conflat vacuum flange on the service ring Remove the motor mount assembly including motor Helical coupling travel...

Page 62: ...tion of the post Gently lift the cover off being careful not to damage the wires connected to it To remove the V plate the test mass must be partially disassembled First note the orientation of the top part of the test mass and the V plate It is very important to replace these parts in the same orientation Remove the three beryllium copper M3 screws that secure the top part of the test mass to the...

Page 63: ...om the rod Remove the ribbon cable wires connected to the cart Remove the ribbon cable clamp on the cart and gently lift the cart off the guide rods Two retaining rings secure each bearing to the cart To remove the rings they must be wound off the end of each bearing Slide the linear bearings out of the cart and slide the new ones in Replace the retaining rings NOTE Venting holes have been added t...

Page 64: ...cture Remove the two screws which fasten the pulley yoke to the bottom rod ring and remove the yoke Remove the bowed retaining ring from the short end of the pulley shaft noting the orientation of the bow Figure 4 1 Drive Pulley Assembly CAUTION DO NOT DEFORM THE BOWED RETAINING RING Remove the retaining ring from the other end of the shaft Slide out the pulley shaft taking care not to lose the Wo...

Page 65: ...y in its groove 4 1 1 10 Replacing the Rotary Shaft Encoder Insert a 1 32 Allen wrench into the access hole at the top right 1 o clock position of the encoder Rotate the shaft until the set screw that holds the disk to the shaft is aligned with the wrench and loosen the screw Pry the main encoder housing off the encoder back plate with a flat blade screwdriver The back plate must remain attached t...

Page 66: ... loosening the locking screw 2 5 mm Allen screw on the slide of the fiber input and moving the slide A properly collimated beam should have a diameter of 6 mm 5 Slide the loosened assembly back into the interferometer note the orientation key and precisely collimate the laser beam by use of the slide until the beam size in the collimating telescope is minimized 6 Tighten the locking screw on the s...

Page 67: ...s are parallel to the telescope axis 16 Verify that the beam is traveling properly through the superspring by making sure the beam enters and exits the superspring through the two holes in the alignment fixture 17 If the beam is not traveling properly through the superspring verify that the reference beam is centered in the fringe viewer and verticality is correct 18 Using mirror 2 make the test a...

Page 68: ...bsolute value A digital voltmeter or oscilloscope is recommended for this procedure In both the X and Y directions there should be a plateau of stable less negative voltage Adjust both the X screw accessed through a hole on the rear of the I B and Y screw accessed by grabbing the knurled knob of the XY stage so that the APD is in the center of both plateaus 24 Replace the rear plate on the interfe...

Page 69: ...OUGH THE SERVICE RING The top flange and Superspring cover may be removed as a unit by removing the six screws holding the cover to the top of the service ring and lifting the cover assembly straight up Most routine maintenance can be accomplished at this point except for replacing the coil linear actuator the mainspring itself and its upper hanger To accomplish these tasks the service ring and bo...

Page 70: ...ws securing the base plate of the Superspring structure to the bottom flange 4 3 1 3 Replacing the Coil Linear Actuator The permanent magnet assembly of the coil is attached to the base plate and the voice coil pusher is attached to the emitter detector block of the support structure Remove the service ring as described previously Remove the base plate by loosening the three 3mm barrel clamp screw...

Page 71: ...st mass to drop BE VERY CAREFUL NOT TO BEND THE FILAMENT WIRE IN THIS ASSEMBLY It is highly recommended that this procedure be done at Micro g Solutions 4 3 1 5 Replacing the Flexures Necessary tools and fixtures A small table with leveling screws that can hold the Superspring in the field one could use the entire tripod or just the leveling feet A pulling tool music wire 16 long with m 1 6 thread...

Page 72: ...port springs from O rings and remove lower triangular spring plate This plate is held on by four 3 mm screws Be careful not to cut or score the O rings Note orientation of emitter detector block and remove block six 3mm screws in deep counter bore holes Note The test mass spring and flexure will come out with the emitter detector block Wear plastic gloves when handling copper test mass to prevent ...

Page 73: ...Adjustment and Maintenance 4 coarse adjustment screw travel Rotate test mass so beam holes in top lever and copper test mass roughly match 4 17 ...

Page 74: ...o shoulder screws then tighten 6mm screws Install electrical feedthrough Re connect all electrical connections Level the Superspring by viewing on each side of copper mass and centering in cage place entire Superspring on an adjustable table to change where the mass hangs Note that the mass should hang down approximately 1 5mm from the point where it makes contact with the top of the cage assembly...

Page 75: ...e bushing out of the way The screws holding the motor to the motor mount are now accessible and can be removed Reverse the procedure to install the new motor 4 3 1 8 Adjusting the Micro Switches Adjust the trip positions of the micro switches that control the limits of travel of the focus adjustment motor by changing the position of the set screws in the actuator arms The limit switches should shu...

Page 76: ...ions for parts and procedures THE POSITION OF THE DELTA RODS DETERMINES THE CLEARANCE BETWEEN THE VOICE COIL PUSHER AND THE MAGNET ASSEMBLY IT IS IMPERATIVE THAT THE ASSEMBLY NOT RUB OR DRAG To field check the alignment measure the gap between the support structure pins and the center tube assembly with a feeler gauge This gap should be equally spaced approximately 003 005 all around If the suppor...

Page 77: ...ser lambda over two λ 2 As the velocity of the falling object changes the frequency f of the fringe signal is swept according to f 2gt λ where g gravity and t time The optical fringes are detected by an APD mounted in the interferometer base The zero crossings of the fringes provide very good fiducial marks which can be used for timing The zero crossing points of the a c coupled fringe signal are ...

Page 78: ...Adjustment and Maintenance 4 4 22 ...

Page 79: ... directly on the board The APD s high oltage bias is zener limited to 600 volts on board A potentiometer is used to set the voltage supplied to the APD The analog output is buffered by an OP AMP directly from the APD The zero crossing of the fringe signal is determined by the high speed comparator which in turn drives a 50 Ω line driver chip A 40 mV hysteresis is implemented on the discriminator t...

Page 80: ...supplied from the 15V supply and is connected to J3 J5 and J6 of the APD board Table 4 1 4 4 1 3 Rubidium Oscillator The FG5 uses a rubidium oscillator as a frequency standard atomic clock The oscillator generates a 10 MHz sine wave with amplitude of 5Vrms into 50 Ω It is used by the TIA card in the personal computer to provide accurate time information The clock is located in the power supply mai...

Page 81: ...m EXT ARM BNC Patch Panel trigger out External Trigger External Clock EXT CLK BNC Power Supply 10 MHz External Clock 4 5 DROPPER CONTROLLER The dropper controller is a flexible control circuit programmable servo controller that can direct the motor to servo the cart and test mass to a specified height in the dropping chamber using a rotary shaft encoder or to a specific velocity again using the sh...

Page 82: ...ree bits of latched data a total possibility of eight modes Each mode can have an associated four bit state machine cycle sixteen possible states A counter which can be clocked by an external signal the computer by a window comparator level or by a programmable reference level in the dropping chamber controls the latter four bits These clock choices are stored in the first EPROM This architecture ...

Page 83: ...MAY INDICATE SYSTEM FAILURE 4 5 1 2 MANUAL 4 5 1 2 1 To Select THIS MODE SHOULD NOT NORMALLY BE NEEDED BY THE USER AND SHOULD NOT BE USED WITHOUT FULL UNDERSTANDING OF THE CONTROLLER This mode is selected by turning the front panel selector switch to MANUAL and pressing the INIT button 4 5 1 2 2 Function The front panel potentiometer controls a servo position for the cart The cart servo will not i...

Page 84: ...ecreasing ramp velocity servo until about 5 mm At this point the state machine returns to the standby mode 1 4 5 1 4 OSCILLATE 4 5 1 4 1 To Select Press INIT while the selector switch is set to OSC 4 5 1 4 2 Function This mode causes the cart to move up and down smoothly with a constant velocity in the dropping chamber It is very useful for generating fringes DO NOT LEAVE IN OSC MODE UNATTENDED Cu...

Page 85: ... level settings that trigger different phases of the servo The output of the DAC is available on the front panel BNC called CART position The DAC output has a programmable offset corresponding to either 1 the manual position controlled by the front panel knob or 2 the hold position trimpot on the controller board The servo adds in some derivative or damping that is set by the CART DAMP trimpot on ...

Page 86: ...sition between the cart and test mass The signal is preconditioned by a preamplifier mounted on the cart The position can be monitored on a front panel BNC labeled SPHERE The servo consists of an active feedback servo and a passive feedforward servo The feedforward provides the approximate correct motor voltage during the drop This reduces the demands on the feedback servo 4 5 2 4 Active Sphere Se...

Page 87: ...d lowering the mainspring and an electromagnetic coil that enhances the natural frequency of the mainspring by 2000 to 3000 percent Inside the Superspring are an SE 3455 infrared LED a photo detector and a sphere signal preamplifier An infrared beam from the LED shines through an optical glass sphere attached to the bottom of the Superspring mass which is suspended from the end of mainspring The s...

Page 88: ...er has six main parts 1 LED driver 2 Sphere signal buffer 3 Window comparator 4 Motor driver 5 Active filter 6 Coil driver The LED driver supplies a constant current to drive the LED in the Superspring can This current can be adjusted internally using the potentiometer pot The sphere signal buffer buffers the signal from the Superspring can so it can be routed to different parts of the board The S...

Page 89: ...is zero 4 6 1 2 3 WINDOW The Superspring controller will activate the motor when the sphere voltage is out of range larger than the window setting The motor drives the sphere voltage to zero and then is turned off In principal the Superspring can be left in this mode but it could re zero during a measurement causing excess noise 4 6 1 2 4 REMOTE The Superspring can be made to zero using an externa...

Page 90: ...el 4 6 2 Maintenance Schedule To keep the instrument at its optimum performance level proper maintenance procedures should be periodically performed 4 6 2 1 Annually Inspect replace and adjust the cart drive belt Inspect replace and lubricate the drive system bearings Inspect and replace the tungsten support contacts on the test mass and cart Reassemble the vacuum system and test for leaks Pump do...

Page 91: ...e set up and operated with the utmost care to achieve optimum results It is especially important to maintain a system check log during set up and observation Conscientious recording of system information e g laser power ambient temperature and atmospheric pressure Superspring position ion pump current fringe signal amplitude dropping chamber and Superspring level positions etc can be extremely hel...

Page 92: ...fluidic rotary feedthrough needs to be replaced Vacuum level ion pump current consistently high This can be caused by a small leak in the dropping chamber usually at an O ring seal Also the ion pump may need to be replaced Leak check the dropping chamber If no leaks are found replace the ion pump The life of the Ion Pump is rated as 20 000 hours at 1 x 10 6 torr continuous operation However ion pu...

Page 93: ... verticality of the beam is drifting Single clicking sound during lift and drop Drive belt developing fracture and needs to be replaced Stops after one drop and resets itself Drive belt could be loose and may need to be tightened Multiple clicking sounds during lift and drop Drive bearing needs to be replaced Cart drives to the top very fast No shaft encoder signal Check cable connection Check tha...

Page 94: ...number of drop outs The cart travel is not aligned with the vertical The bubble levels on the tripod need to be reset or the dropping chamber is not sitting in the tripod tray correctly Dropper guide rods are not straight Can be due to snubbers tightened asymmetrically or because of stress from bad alignment of rods in the top ring Table 5 1 Dropping Chamber Problems and Solutions 5 4 ...

Page 95: ... related to the interferometer Problem Solution WEO laser not producing beam Check cable connections If the front panel show no sign of power check the fuse and power switches WEO laser power too low Laser optics need cleaning Alignment of back laser mirror should be adjusted Iodine cell needs rotation adjustment to maximize beam Laser tube needs to be replaced Fiber alignment needs to be optimize...

Page 96: ...t of faraday isolator to increase beam intensity Analog fringe output clipped with alignment optimized Intentionally mis align the input into the fiber optic Set fringes at about 340 mV Larger than expected single drop distributions or multi node histogram on computer display or simply too large of a scatter at a quiet site 100µGal This can be due to the software incorrectly detecting a peak hop R...

Page 97: ...es at all No power to APD One both beam blockers are pushed in Very bad alignment of the test reference beams Look into the telescope and make sure that the test and reference beams are overlapped Also make sure that the beams are overlapped in the fringe viewer with the twiddler Fringe amplitude varies as the cart is moved up or down The iodine stabilized laser is running multi mode This can indi...

Page 98: ... the change in gravity is negative the spring should be driven down into range It is always very important to monitor the voltage at the front panel BNC of the Superspring controller marked SPHERE OUT while the servo loop is still open The sphere position should be moving substantially voltage when the loop is open and the Superspring is unlocked This indicates that the test mass is hanging freely...

Page 99: ...been damaged and needs replacement The lock on the controller is locked Gravity is extremely noisy mGal It is possible that there is an earthquake event occurring somewhere on earth The Superspring is very sensitive to earthquakes no matter where they occur The gravity will continue to be noisy for hours or even days when the earthquake event is close to the gravimeter location Table 5 3 Superspri...

Page 100: ...ections of the cards to the computer Problem Solution g responds with Time Out Check Trigger Fringe Amplitude TTL Cable message General message indicating no fringe data arrived at the computer Check for alcohol pool in the I B beam blocker pushed in TTL cable to computer TRIG cable from dropper controller to computer Check that the fringe amplitude is 250 mV Check that the dropper is functioning ...

Page 101: ...controller the majority of problems encountered with this system have been poor or missing connections during setup Table 5 5 Electronics Problems and Solutions Problem Solution A systematic gravity shift is observed The rubidium clock has lost its calibration Check its frequency against a standard Cesium reference Beam verticality is off Beam is not collimated High rotation translation of test ma...

Page 102: ...ttraction corrections accurate to better than one µGal can still be computed and applied during post processing Possible problems and solutions pertaining to the environmental sensors package are shown in Table 5 6 Problem Solution Gravity is 300µGal too high The system is not reading the barometer Make sure the barometer is hooked up correctly Also make sure that the voltage range for the analog ...

Page 103: ...o determine if there is excessive rotation of the test mass about a horizontal axis i e if the balls and or v grooves are worn and need to be replaced Possible problems and solutions are shown in Table 5 7 Problem Solution Excessive Rotation 10mrad sec Alignment of the dropper is not correct Ball Vee contacts for the test mass need to be replaced Table 5 7 Rotation Monitor Problems and Solutions 5...

Page 104: ...s much as possible A basement with a thick concrete floor is usually best Avoid floors with composition materials if possible and set up the instrument on a solid tile or concrete floor 5 3 3 ENVIRONMENTAL NOISE Heavy heating or cooling equipment as well as bipedal or vehicular traffic can cause vibrations which tend to increase the drop to drop scatter of the observations This can usually be seen...

Page 105: ...est to use voltage stabilizers and or uninterruptible power supplies to minimize problems with unreliable line voltage Some system components especially the WEO Model 100 iodine laser and system computer are more sensitive to line voltage fluctuations than others so it is always best to stabilize line voltage well enough to satisfy the requirements of the most sensitive component 5 15 ...

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Page 107: ...0 60Hz 100 115 220 and 240 VAC 1 Remove AC power cord from the power entry module on the rear panel of the laser controller 2 Open the power entry module and remove drum voltage selector IT IS VERY IMPORTANT TO REMOVE THE DRUM DO NOT ROTATE THE DRUM IN PLACE THIS CAN CAUSE DAMAGE TO THE TRANSFORMER INSIDE THE LASER CONTROLLER 3 Rotate the drum voltage selector until the proper line voltage is visi...

Page 108: ...ly is compatible with AC voltages of 110 and 240 VAC 50 60Hz No manual switching is necessary 6 3 Computer Computer models are prone to change as newer technology is introduced The computers are usually very easy to switch voltages by flipping a selector switch near the AC power cord Some models use a universal power supply so switching is not required Please check the computer manual supplied wit...

Page 109: ...ted The required pumping time is determined by the time the ion pump has been off power and the temperature at which the dropping chamber has been stored If the ion pump has been off for less than one week a pumping time of 1 hour or less is usually sufficient to start the ion pump When the ion pump has been off for several weeks it is usually best to pump the chamber overnight 12 14 hours It may ...

Page 110: ...ble together Make sure that there is no dirt or hair on the vacuum flanges or O ring and take care not to touch the inside of the rings or hose Sometimes it is helpful to use a little high vacuum grease such as Apiezon on the O ring to ensure a good seal There are two different circumstances which dictate whether the bellows valve is to be open or shut when starting the turbo pump If the chamber i...

Page 111: ...e using the type F thermocouple cables which are attached to the dropping chamber Make sure that the temperature probe is contacting both the heat tape and the chamber This insures that the hottest part of the chamber does not exceed the maximum temperature Bake the chamber for at least 8 hours with the turbo pump running It is very important to have the test mass locked down during bake out and c...

Page 112: ...n five minutes after turning on the ion pump At operating pressure nominal voltage is 4 KV on AC and 3 KV on battery If the ion pump has not started within five minutes turn off the power and continue pumping with the turbo pump for at least one hour before trying the ion pump again Leaving the ion pump on with excessive current 10 5 Torr shortens the lifetime of the pump dramatically Once the ion...

Page 113: ...mirror Use the travel lock pin to lock the mass in this position Adjust only mirror mount 1 so as to put the laser beam back in the center of the test mass mirror Lower the test mass to the bottom and adjust only the beam splitter on mirror mount 2 to put the spot back in the center of the test mass mirror The first mirror is used to translate the beam onto the mirror at the top position and the b...

Page 114: ...The Rotation Monitor Appendix C extra reflection from the glass viewport will interfere with the measurement Any extraneous reflections can be blocked with a piece of paper or tape 8 2 ...

Page 115: ...ost processing and troubleshooting the system This appendix consists of several checklists and logs which are helpful In many cases the user may develop additional or modified procedures which are tailored to their own survey methodology 9 1 Switching the AC Power Switching the AC Power Checklist Determine and use proper fuse for each component WEO 100 Laser Use drum in power entry module Remove d...

Page 116: ...wer switches Turn on laser power Place superspring tripod over reference mark Rough level superspring tripod Measure and record lower reference height Place superspring on tripod and clamp in position Level superspring using precision level vials Remove superspring dust cover and place interferometer on superspring Tighten four knobs to lock interferometer to superspring Remove dust cover from int...

Page 117: ...d adjust if necessary Place blue pads and tripod feet under dropping chamber tripod Raise each foot until it contacts nylon ball on tripod leg Raise dropper two revolutions of each tripod foot Level dropper cross level first then long level Check superspring levels and adjust if necessary Measure and record upper reference height Place computer system controller on electronics case Connect compute...

Page 118: ... WEO Model 100 Laser only Connect BNC cable from sphere out on superspring controller to Channel 1 on patch panel Connect BNC cable from meter monitor on ion pump power supply to Channel 2 on patch panel Connect BNC cable from trigger out on patch panel to Trigger EXT IN on dropper controller Make sure dropper controller is on STANDBY Connect dropper signal cable white Lemo connector from power su...

Page 119: ...perspring position 0 20 mV and turn coil switch on Adjust beam verticality and optimize fringe signal Check set computer time Edit fields in Process Setup Set dropper controller to AUTO and initiate Table 9 2 FG5 Setup 9 3 Dropping Chamber Pump Down and Bake Out Dropping Chamber Pump Down and Bake Out Set turbo pump for proper line voltage see appendix A Place turbo pump on case lid and connect pu...

Page 120: ...et package from ion pump if heating is required Connect heat tape and temperature sensors to dropper and ion pump if heating is required Lock test mass Monitor dropper and ion pump temperatures dropper 80 C Bake dropper and ion pump for at least 8 hours Turn off heat tapes Allow dropper to cool at least 16 hours Unlock test mass Reinstall ion pump magnet package Connect HV and ground cables betwee...

Page 121: ...m vacuum valve Unlock valve locking ring and slowly open valve Vent with dry nitrogen if possible Remove top flange Loosen snubber lock nuts and screws Remove chamber cover from service ring Keep bottom flange clean and protect O ring surface Table 9 4 Removing Dropping Chamber Cover 9 4 2 Replacing Dropping Chamber Cover Replacing Dropping Chamber Cover Checklist Inspect chamber O ring and sealin...

Page 122: ...dropper adjust level bubbles on tripod tray Table 9 5 Replacing Dropping Chamber Cover 9 4 3 Replacing Drive Belt Replacing Drive Belt Checklist Remove dropping chamber cover Loosen belt tension Remove belt clamp from cart Remove belt Clean drive and top pulleys and wipe new drive belt Thread new belt around top and drive pulleys Place belt ends over dowel pin and install belt clamp do not tighten...

Page 123: ...w until belt is straight Tension belt by tightening adjustment screw three turns until tension spring is just short of coil bind or tension belt using torque wrench Table 9 7 Adjusting Belt Tension 9 4 5 Replacing Ferrofluidic Vacuum Feedthrough Replacing Ferrofluidic Vacuum Feedthrough Checklist Remove dropping chamber cover Loosen 4 40 screws on Helical coupling between motor and feedthrough Rem...

Page 124: ...ing from feedthrough Unscrew feedthrough from Conflat flange Lubricate O ring on new feedthrough Gently tighten new feedthrough to Conflat flange use pliers with padded jaws Table 9 8 Replacing Ferrofluidic Feedthrough 9 4 6 Replacing V plate Replacing V plate Checklist Remove dropping chamber cover Remove bottom drag free cover from cart Detach LED bracket from cart and pull out of the way be car...

Page 125: ...ts which pass through V plate Lower bottom part of test mass through V plate Remove old V plate and replace with new one Reverse procedure to reassemble Table 9 9 Replacing V Plate 9 4 7 Replacing the Linear Bearings Replacing Linear Bearings Checklist Remove dropping chamber cover Remove drive belt Remove top rod ring Remove upper bumper stop assembly Remove ribbon cable wires and clamp from cart...

Page 126: ...bearings out of the cart Make sure new linear bearings have venting holes Make sure new linear bearings have been cleaned and lubricated with Krytox 143AC low vapor pressure oil Insert new linear bearings in cart and insert retaining rings Reverse above procedure to replace cart Table 9 10 Replacing Linear Bearings 9 12 ...

Page 127: ...nd Ferrofluidic feedthrough Remove screws holding bottom rod ring to bottom flange Rotate guide rod structure so shaft clears service ring Remove guide rod structure Remove pulley yoke from bottom rod ring Remove bowed retaining ring from short end of pulley shaft note orientation Remove retaining ring from other end of shaft don t lose Woodruff Key Remove pulley from bearing mounting yoke Push be...

Page 128: ... Pulley Replacing Shaft Bearings Top Pulley Remove dropping chamber cover Remove drive belt Remove snap rings on upper bump stop and slide down shaft Remove retaining rings on top of upper pulley yoke Remove pulley slide down Remove bowed retaining ring from short end of pulley shaft note orientation Remove retaining ring from other end of shaft Remove pulley from bearing mounting yoke Push bearin...

Page 129: ... Pulley 9 4 10 Replacing Rotary Shaft Encoder Replacing Rotary Shaft Encoder Checklist Loosen set screw holding disk to shaft Pry encoder housing off back plate plate remains attached to travel lock plate Snap new encoder over back plate Tighten set screw holding disk to shaft Rotate shaft to assure encoder disk rotates freely Table 9 13 Replacing Rotary Shaft Encoder 9 15 ...

Page 130: ...ocking screw Remove dust plug from interferometer base Place dropping chamber and tripod on interferometer base Loosen two set screws above fiber optic input and block test beam Center beam in fringe viewer by translating fiber optic input Tighten set screws Focus telescope crosshairs and center beam in telescope viewfinder by adjusting mirror 3 Open side access door and place alcohol container in...

Page 131: ... telescope Adjust twiddler to align test and reference beams in fringe viewer Remove dropping chamber and tripod from interferometer base Block test beam and remove top plate of interferometer base Adjust APD X Y stage to maximize voltage at analog BNC connector on interferometer base largest negative voltage Replace top lid of interferometer base and tighten all screws Table 9 14 Interferometer A...

Page 132: ...t remove top flange Lift cover straight up over Superspring mechanism Table 9 15 Removing Superspring Cover 9 6 2 Replacing Superspring Cover Replacing Superspring Cover Checklist Check O ring seat and lubricate O ring if necessary Gently lower Superspring cover including top flange over mechanism Tighten screws holding Superspring cover to service ring Table 9 16 Replacing Superspring Cover 9 18 ...

Page 133: ...n connector Remove travel lock knob Remove travel lock assembly from service ring Remove service ring and bottom flange as a unit Table 9 17 Removing Superspring Service Ring 9 6 4 Replacing Superspring Coil Replacing Superspring Coil Checklist Remove service ring Remove base plate Lift rod assembly off bottom plate Remove travel lock fork from main rod Unhook support springs from O rings Remove l...

Page 134: ...ing Superspring Coil 9 6 5 Replacing Superspring Flexures Replacing Superspring Flexures Checklist Remove Superspring cover Put dust cover over top main tube Remove service ring Place hard foam or rubber shim between top rod ring and top triangular plate Fasten plates together with cable tie Loosen clamps holding rods to bottom plate Disconnect wires from pre amp circuit board Lift rod assembly of...

Page 135: ...ic gloves when handling test mass Remove spring from test mass count number of spring turns holding upper anchor to main spring Put lower lock nut on new flexure assembly Remove broken flexure anchor Screw new flexure anchor into spring to original position Thread pulling tool through one nut top lever and down center tube Thread tool into top of flexure coarse adjustment screw of main spring asse...

Page 136: ...d test mass Table 9 19 Replacing Superspring Flexures 9 6 6 Assembling Superspring Assembling Superspring Checklist Replace emitter detector block in original orientation below lever pivots Replace lower triangular spring plate Attach support springs Install travel lock fork assembly on shaft Replace spring assembly into lower plate don t damage coil Make sure rods are seated flush with bottom of ...

Page 137: ...rews Replace travel lock assembly Rotate main spring assembly to equalize travel lock fork clearance Tighten screws holding spring assembly to service ring Install electrical feedthrough Connect all wires match color coding Place Superspring on leveling table Adjust table to center test mass in cage Make sure top of test mass is about 1 5 mm below cage assembly Connect Superspring controller to Su...

Page 138: ...Checklists and Logs Appendix D Measure gap between two levers near ZPM 9 24 ...

Page 139: ...g of test mass in cage and adjust bubble levels Table 9 20 Assembling Superspring 9 6 7 Replacing Superspring Focus Lever Motor Replacing Superspring Focus Lever Motor Checklist Remove nut on focus adjustment screw Lower focus lever motor assembly off fulcrum lever Loosen set screw holding hex bushing to motor shaft Raise bushing out of the way Remove screws holding motor to motor mount Reverse pr...

Page 140: ... lever and fulcrum plate is 4 8 mm Table 9 22 Adjusting Superspring Micro Switches 9 7 Packing the FG5 Packing the FG5 Checklist Unplug cables from electronics rack and components If leaving the chamber under ion pump control leave ion pump cables attached from power supply to dropping chamber Put remaining cables in zippered pouch inside of rear electronics case lid Secure lids to electronics cas...

Page 141: ...ews in top dropper flange Replace viewing port cover Dropping Chamber Engage cart travel lock Remove dropping chamber from tripod and place in dropping chamber case Place ion pump controller and cables in dropping chamber case too Lift tripod from interferometer base Remove legs and store in dropping chamber tripod case Place brass feet in superspring case and blue pads in dropper tripod case Plac...

Page 142: ...pring Remove superspring from tripod and place in superspring case Close superspring case and secure all latches Place superspring tripod in its case Close interferometer case and secure latches Make sure all blank flanges and covers are in place on turbo pump and flexible tube Store flexible tube and power cord in base of turbo pump case Place turbo pump in its shipping case Close turbo pump case...

Page 143: ...Checklists and Logs Appendix D This Page is Intentionally Blank 9 29 ...

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Page 145: ...perspring 9 22 FG5 Setup 9 2 Interferometer Alignment 9 16 Packing the FG5 9 25 Pump Down and Bake Out 9 5 Removing Dropping Chamber Cover 9 7 Removing Service Ring Superspring 9 19 Removing Superspring Cover 9 18 Replacing Drive Belt 9 8 Replacing Ferrofluidic Feedthrough 9 9 Replacing Flexures 9 20 Replacing Lever Focus Motor 9 24 Replacing Linear Bearings 9 11 Replacing Rotary Shaft Encoder 9 1...

Page 146: ...g 3 16 Setting Up 3 1 FG5 Software 2 15 FG5 System 2 1 FG5COMND DAT File Editing 3 16 FG5PARAM DAT File Editing 3 16 Filter Active 4 31 Flanges Conflat 2 6 Flexures 2 12 Replacing 4 15 Focus Lever Motor Replacement 4 18 Frequency Standard 4 22 Fringe Interference 2 8 Fringes Optical 4 20 Optimizing 3 14 Zero Crossings 4 20 H Hardware Optional 2 15 Required 2 15 Height Term Instrument 3 9 I Install...

Page 147: ...s Package 2 15 Rotation Monitor 2 15 Optional Systems 2 20 O Ring Lubrication 4 4 O Rings Inspection 4 2 Lubrication 4 2 P Packing Dropping Chamber 3 21 Dropping Chamber Tripod 3 21 Electronics 3 19 FG5 3 19 Interferometer 3 21 Rotation Monitor 3 20 Superspring 3 22 System Controller 3 20 Turbo Pump 3 22 Photo Detector 2 19 Position Cart 4 27 Power Shutting Off 3 18 Power Mains Module 2 20 Power S...

Page 148: ...e Stability 5 15 Snubbers Tightening 4 2 Soft Catch 2 8 Software 2 15 Sphere Optical Glass 2 4 Sphere Detection System Superspring 2 14 Sphere Detector System Superspring 2 12 2 19 Sphere Servo 4 28 Sphere Signal Buffer 4 30 Starting the Ion Pump 7 4 Superspring 2 13 Assembly 4 17 Controller 4 29 Function 2 1 2 12 Leveling 3 11 Packing 3 22 Releasing Travel Lock 3 12 Removing the Cover 4 13 Setup ...

Page 149: ...rence Height Measuring 3 9 UTIC Function 2 8 V Vacuum Valve 2 6 Valve Vacuum 2 6 Velocity Cart 4 27 Venting the Dropping Chamber 4 1 Vertical Adjustment Test Beam 3 14 Verticality Dropper 3 8 Viewing Port Function 2 7 V Plate Replacement 4 5 W WEO 100 Laser 2 9 Setup 3 3 Shutting Down 3 18 Switching AC Power 6 1 Window Comparator 4 30 Z Zero Position Superspring 2 19 Zero Crossings Fringes 4 20 Ze...

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