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The Constant Fraction Discriminators CFD8c, CFD7x, CFD4c, CFD1c and CFD1x (11.0.1701.1) 

Page 24 of 25  

List of Figures 

F

IGURE 

3.1

B

:

 

T

HE 

CFD8

 

(

HERE

:

 

CFD8

B VERSION

),

 

CFD7

X SIMILAR

 .................................................................................... 6

 

F

IGURE 

3.2

B

:

 

P

HOTOS OF THE 

CFD4

 AND 

CFD1

 SERIES CASES 

(

HERE

:

 

B

 VERSIONS

)

 AND THE 

SPS3

 POWER SUPPLY

 .......... 7

 

F

IGURE 

3.3

B

:

 

F

RONT PANEL INPUTS

,

 TEST POINTS AND CONTROL POTENTIOMETERS 

,

 NOT SHOWN IS THE VETO INPUT  AND 

THE 

CFD

 FRACTION

 POTENTIOMETER BEING ON THE FRONT PANEL FOR C AND X VERSIONS 

(

SEE 

F

IGURE 

3.14) ............. 8

 

F

IGURE 

3.4

B

:

 

S

CHEMATICS OF A 

CFD

 ANALOGUE CHAIN

 ...................................................................................................... 8

 

F

IGURE 

3.5

B

:

  TOP

/

SIDE PANEL WITH FRACTION POTENTIOMETER ONLY VERSIONS A

/

B

)

  AND OPTIONAL JUMPER  TERMINAL 

FOR INCREASING THE 

CFD

 OUTPUT WIDTH BY A FACTOR OF 

10

 

(

OPTIONAL

) ................................................................. 9

 

F

IGURE 

3.6

B

:

 

S

CHEMATICS OF THE  

CFD

 DIGITAL CIRCUIT CHAIN

 ......................................................................................... 9

 

F

IGURE 

3.7

B

:

 

O

SCILLOSCOPE  TRACES OF IN

-

  AND OUTPUT SIGNALS OF THE 

CFD,

  TRACES 

1-4

  FROM TOP

:

  INPUT SIGNAL

,

 

ANALOGUE MONITOR OUTPUT SIGNAL

,

  DIGITAL MONITOR OUTPUT SIGNAL

,

 

CFD

  TIMING OUTPUT SIGNAL 

(

WHICH 

TRIGGERS ALL TRACES

).

 

T

HE RED ARROWS INDICATE THE 

TIMING TRANSITION

  WHICH APPEARS SLIGHTLY SHIFTED IN 

THE DIFFERENT TRACES DUE TO INTERNAL DELAYS

.

 

T

HIS AND THE FOLLOWING IMAGES OF SIGNAL TRACES HAVE BEEN 

OBTAINED WITH A 

300 MH

Z ANALOGUE OSCILLOSCOPE 

(

A LARGE NUMBER OF SIGNALS WITH VARYING PULSE 

HEIGHTS ARE SUPERIMPOSED

).

 

S

IMILAR VIEWS  CAN BE OBTAINED FROM DIGITAL OSCILLOSCOPES WITH ADEQUATE 

PERSISTENCE

 SETTING

 .............................................................................................................................................. 10

 

F

IGURE 

3.8

B

:

 

S

IGNAL TRACES SIMILAR AS IN 

F

IGURE 

3.7

B FOR POORLY ADJUSTED 

T

HRESHOLD LEVEL

:

 ANALOGUE MONITOR 

OUTPUT

,

  DIGITAL MONITOR OUTPUT 

(

ONLY IN LEFT PICTURE

)

  AND 

CFD

  OUTPUT

.

 

L

EFT PICTURE

:

  FOR TOO HIGH 

THRESHOLD SETTINGS ONLY INPUT SIGNALS WITH VERY HIGH AMPLITUDES ARE REGISTERED

.

 

W

HEN SETTING THE 

CORRECT 

T

HRESHOLD LEVEL

,

 THE DARK AREA SHOWN BY THE ARROW WOULD BE FILLED WITH SMALLER AMPLITUDE 

SIGNALS

.

 

R

IGHT PICTURE

:

 THRESHOLD SETTING TOO LOW 

(

I

.

E

.

 IN THE NOISE

) ............................................................. 11

 

F

IGURE 

3.9

B

:

 

S

IGNAL TRACES 

(

AS IN 

F

IGURE 

3.8

B LEFT

)

  BUT WITH TOO LONG 

(

LEFT PICTURE

)

  AND TOO SHORT DELAY 

CABLE 

(

RIGHT

) ............................................................................................................................................................. 12

 

F

IGURE 

3.10

B

:

 

S

IGNAL TRACES 

(

AS IN 

F

IGURE 

3.8

B LEFT

)

  WITH A TOO SHORT DELAY CABLE 

(

LEFT PICTURE

).

 

T

HIS CAN 

FAIRLY BE COMPENSATED BY INCREASING THE 

CFD

 FRACTION FROM 

0.35

 TO 

0.6

 

(

RIGHT PICTURE

) ........................... 12

 

F

IGURE 

3.11

B

:

 

S

IGNAL TRACES 

(

AS IN 

F

IGURE 

3.8

B LEFT

)

 WITH DIFFERENT 

CFD

 FRACTIONS

:

 LEFT PICTURE F 

=

 

0.35,

 RIGHT

:

 

=

 

0.7 .......................................................................................................................................................................... 13

 

F

IGURE 

3.12

B

:

 

S

IGNAL TRACES 

(

AS IN 

F

IGURE 

3.8

B LEFT

)

  WITH THE WALK LEVEL  SET TO THE BASELINE  OF THE INPUT 

SIGNALS  

(

LEFT PICTURE

)

 AND SLIGHTLY TOWARDS THE POSITIVE SIDE WHERE THE NOISE TRIGGERS BEGIN TO VANISH 

(

RIGHT PICTURE

),

 LEADING TO SLIGHTLY LESS INTENSITY IN THE AREA RIGHT OF THE ARROW

.................................... 13

 

F

IGURE 

3.13

B

:

 

S

IGNAL TRACES 

(

AS IN 

F

IGURE 

3.8

B LEFT

)

 WITH THE 

W

ALK LEVEL  SET TOO LOW 

(

LEFT PICTURE

)

 AND TOO 

HIGH 

(

RIGHT PICTURE

) ................................................................................................................................................. 14

 

F

IGURE 

3.14

B

:

 

P

OSITION OF 

V

ETO INPUT SOCKET ON THE 

CFD8

C FRONT PANEL

.

 

F

OR THE 

CFD4

C IT IS FOUND ON THE REAR 

PANEL

 .......................................................................................................................................................................... 15

 

F

IGURE 

3.15

B

:

 

T

RACE  OF THE INPUT SIGNAL  TO THE 

V

ETO SOCKET 

(

UPPER TRACE

)

  AND SIGNAL TRACES OF 

CFD

  TIMING 

SIGNALS 

(

LOWER TRACE

,

 INTEGRATED OVER MANY EVENTS

)

 FOR 

V

ETO 

(

LEFT

)

 AND 

G

ATING MODE 

(

RIGHT

) .............. 15

 

F

IGURE 

3.16

B

:

 

J

UMPER 

B

LOCK 

(

HERE

:

  INSIDE 

CFD1

C

)

  FOR DEFINING THE LOGIC MODES

:

 

V

ETO 

(

LEFT PICTURE

,

  DEFAULT 

SETTING

),

 

G

ATING 

(

MIDDLE PICTURE

)

 AND 

N

EUTRAL 

(

RIGHT PICTURE

) ...................................................................... 15

 

F

IGURE 

3.17

B

:

 

F

RONT AND REAR PANEL OF 

CFD1

C WITH MARKED SCREWS

 ....................................................................... 16

 

F

IGURE 

3.18

B

:

 

F

RONT AND REAR PANEL OF 

CFD8

C WITH MARKED SCREWS

 ....................................................................... 16

 

F

IGURE 

3.19

B

:

 

I

NSIDE VIEW OF THE 

CFD8

C WITH JUMPER BLOCKS MARKED BY YELLOW CIRCLES 

(CFD7

X SIMILAR

) ........ 17

 

F

IGURE 

3.20

B

:

 

S

IDE PANEL OF 

CFD4

C WITH MARKED SCREWS

 ........................................................................................... 17

 

F

IGURE 

3.21

B

:

 

O

SCILLOSCOPE TRACES 

(

AS IN 

F

IGURE 

3.8

B LEFT

)

  WITH LESS

-

THAN

-

OPTIMAL 

CFD

  SETTINGS WHICH LEAD 

TO PRE

-

TRIGGERING FOR SOME INPUT SIGNALS

.

 

A

S THE OSCILLOSCOPE IS TRIGGERED BY THE 

CFD

  TIMING OUTPUT 

SIGNAL HERE

,

  THE MONITOR OUTPUT TRACES FOR THESE PRE

-

TRIGGER EVENTS 

(

MARKED READ ARROW

)

  APPEAR 

DELAYED COMPARED TO THE PROPERLY TIMED TRACES

.

 

R

IGHT PICTURE

:

 

T

IME SUM SPECTRA 

(

LINEAR AND LOG 

SCALE

)

 IN PRESENCE OF PRE

-

TRIGGER EVENTS IN AT LEAST ONE OF THE DELAY

-

LINE

S TIMING ELECTRONIC CHANNELS

.

 

S

IMILAR 

SIDE PEAKS

  CAN APPEAR RIGHT OF  THE TIME SUM PEAK 

(

AT LARGER TIME

)

  IF THE 

CFD

  FOR THE 

MCP

 

SIGNAL PRODUCES PRE

-

TRIGGERS

. ............................................................................................................................... 18

 

F

IGURE 

3.22

B

:

 

T

YPICAL IMAGE ARTEFACT CAUSED BY PRE

-

TRIGGER EVENTS 

(

LEFT PICTURE

).

 

T

HESE EVENTS MAY APPEAR 

ONLY ON CERTAIN PARTS OF THE DETECTOR

:

 

A

ROUND THE POSITION X 

=

 

13

  MM SOME EVENTS SEEM  TO BE 

RELOCATED

 

(

SEE RED ARROW

).

  

I

F THE TIME SUM 

(

AS IN 

F

IGURE 

3.21

B RIGHT

)

 IS PLOTTED AS FUNCTION OF POSITION 

(

MIDDLE PICTURE

)

  THE LOCALIZED CONTRIBUTION OF PRE

-

TRIGGER EVENTS IS REVEALED

.

 

S

ETTING A NARROW TIME 

SUM GATE CAN REMOVE THE PRE

-

TRIGGER EVENTS BUT THE IMAGE ARTEFACT 

(

MISSING DATA

)

  REMAINS

,

  SEE RIGHT 

PICTURE

. ...................................................................................................................................................................... 19

 

F

IGURE 

3.23

B

:

 

CFD1

(

LEFT

)

 AND CLOSE

-

UP OF THE 

CFD7

(

RIGHT

)

 SHOWING THE ADDITIONAL  INPUT

/

OUTPUT SOCKETS

,

 

SWITCH AND CONTROL POTENTIOMETERS FOR THE 

CFD

X

 CIRCUIT

 .............................................................................. 20

 

Summary of Contents for CFD1c

Page 1: ...Dek Handels GmbH Supersonic Gas Jets Detection Techniques Data Acquisition Systems Multifragment Imaging Systems The RoentDek Constant Fraction Discriminators CFD8c CFD7x CFD4c CFD1c and CFD1x 11 0 17...

Page 2: ...Kernphysik Max von Laue Str 1 D 60438 Frankfurt am Main Germany Web Site www roentdek com WEEE DE48573152 Product names used in this publication are for identification purposes only and may be tradema...

Page 3: ...3 CFD fraction 12 3b 3 4 Walk level 13 3b 3 5 Output signal width 14 3B 4 THE VETO OPTION 14 3b 4 1 Accessing the jumpers in CFD1c CFD1x 16 3b 4 2 Accessing the jumpers in CFD8c and CFD7x 16 3b 4 3 A...

Page 4: ...Page 4 of 25 The Constant Fraction Discriminators CFD8c CFD7x CFD4c CFD1c and CFD1x 11 0 1701 1...

Page 5: ...Constant Fraction DiscriminatorsCFD8b CFD4b and CFD1b 11 0 1701 1 Page 5 of 25...

Page 6: ...odules containing such boards please review first Chapters 3b 1 to 3b 3 and then refer to Chapter 3b 7 to learn about the difference between the standard CFD and the RoentDek bCFD settings 3b 1 Genera...

Page 7: ...weight 0 8 kg with an external 12 V DC mains adapter for use with 100 250 V AC sockets The power consumption is max 0 5 A at 12 V DC 6 W or max 0 7 A at 12 V DC 10 W for the CFD1x The CFD4c has the s...

Page 8: ...fraction is determined by the choice of fix resistors or a potentiometer as in case of the RoentDek CFDs While one of the signals is inverted later on the other experiences a certain delay CFD delay...

Page 9: ...he signals have to be verified on an oscilloscope The CFD Fraction can be adjusted by another potentiometer labelled Fr on the front panel CFD4b CFD1b side panel CFD8b top lid see Figure 3 6b Figure 3...

Page 10: ...s damped by a factor of 10 For achieving the ideal settings it is first of all important to note that the CFD operates best in all respects and yields the optimal temporal resolution if the input sign...

Page 11: ...delay D of 5 5 ns Note that the RoentDek CFDs will not operate without connecting an external delay cable bridge If the pulse rise time RT is defined as the time from reaching 10 to 90 of the signal m...

Page 12: ...livers the CFD with a standard CFD fraction setting of about 0 35 The CFD fraction can be varied between 0 15 and 1 via a potentiometer In order to observe and quantify the CFD fraction ratio on the o...

Page 13: ...during the bipolar signal s crossover while fluctuating almost equally between high and low states before and long after the signal due to electronic noise on the line not visible in the pictures If...

Page 14: ...idth bridges of the internal circuit see Figure 3 5b With the jumper in place the maximum width is increased to 2000 ns Please contact RoentDek if you are in need of the optional jumpers Obviously a s...

Page 15: ...15b Trace of the input signal to the Veto socket upper trace and signal traces of CFD timing signals lower trace integrated over many events for Veto left and Gating mode right In order to work reliab...

Page 16: ...he front panel 3b 4 2 Accessing the jumpers in CFD8c and CFD7x I Disconnect the mains power supply II On the rear panel remove all five screws red circles Please note that different types and sizes of...

Page 17: ...ear front panel and fix them with all screws and hex bolts 3b 4 3 Accessing the jumpers in CFD4c I Remove all six screws from the right side panel marked in red see Figure 3 20b Figure 3 20b Side pane...

Page 18: ...oscope see Figure 3 21b If a CFD is used for operating a RoentDek delay line detector or similar device these pre trigger events result in a distinct structure in the time sum spectrum see Figure 3 21...

Page 19: ...neighbours 3b 6 The CFDx pulse height determination option The CFDx function is an add on circuit that allows measuring the signal s pulse height The pulse height information is coded as a time delay...

Page 20: ...er trace ramp monitor output the Ramp switch is turned off here Signals are triggered on the CFD timing output signal trace not shown Left and right pictures were obtained with two different cable len...

Page 21: ...Dx signal This is indicated in Figure 3 26b The ramp slope is about 1 V per 12 ns giving an almost linear correspondence between pulse height and time delay with a typically 10 to 20 ns offset for pul...

Page 22: ...iming signal with a RoentDek TDC8HP The same spectrum could be recorded by plotting the time difference between trailing and leading transitions of the CFDx output It is advisable to mark the pulse he...

Page 23: ...se heights will not be registered Please contact RoentDek for advice unless you have received a properly matched system with bFAMP for a certain delay line read out anode Timing signals off the MCP co...

Page 24: ...3 12B SIGNAL TRACES AS IN FIGURE 3 8B LEFT WITH THE WALK LEVEL SET TO THE BASELINE OF THE INPUT SIGNALS LEFT PICTURE AND SLIGHTLY TOWARDS THE POSITIVE SIDE WHERE THE NOISE TRIGGERS BEGIN TO VANISH RIG...

Page 25: ...DTH POTENTIOMETER SETTING LOWER TRACE RAMP MONITOR ALL TRACES TRIGGERED ON THE STOP SIGNAL THE STOP SIGNAL SHOULD BE USED IF THERE IS A SPARE TDC CHANNEL AVAILABLE 21 FIGURE 3 27B AS FIGURE 3 25B RIGH...

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