RoentDek DLD120, Manual

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Page 72 of 80 MCP Delay Line (Version 6.2.90.5)
can be reduced by increasing the CFD threshold and/or by reducing the MCP bias. However, this might also reduce
the detection efficiency for the real particles.
b) more counts that I would expect, but rather diffusely distributed.”
Is there any other source of charged particles/UV photons (ion gauge, corona discharge somewhere in the
chamber)?
c) areas of reduced efficiency.”
The MCP bias might be too low and/or the CFD settings too high, also the electronic amplification might be too
low.
d) sharp lines in the middle of the detector, “ghost” images at left, right, above or below the central image.”
The CFD thresholds are not set properly. The signals induced by some incoming particles are above threshold for
channels 1/2 (MCP start) but not for at least one of the “stop” channels (channels 3-8). Reduce the threshold for
channels 3-8 until you get similar count rate from all channels. Make also sure that none of the CFD channels
triggers in the noise. If the count rate from channels 3-8 differ by more than 10% relative to each other even for
good signal-to-noise ratio and low threshold then it is advisable to adjust the amplifications of the DLATR boards.
PROBLEM:
“All analog output signals (channel 1 or 2 and channels 3-8) look ok but not the CFD outputs
(Tn), at least one of the outputs is missing or has too low/too high count rate.”
ƒ Adjust thresholds until you get similar count rate from all channels. Make sure that none of the CFD channels
triggers in the noise. If the count rate from channels 3-8 differ by more than 10% relative to each other it is
advisable to adjust the amplifications of the
DLATR boards.
ƒ Have amplifiers been damaged due to prior incidents of discharge, power failure, etc.?
ƒ
Is the power source for the (N)DLATR6 strong enough (sufficient current, correct voltage)?
PROBLEM:
“The analog output from the MCP front/back (channels1/2) looks ok but not all of the delay-
line signals (channels 3-8), …
a) all are missing.”
ƒ Make sure that the potentials on “holder”, “signal” and “reference” on are correct.
ƒ
Is there a wiring error? Remove “signal” and “reference” SHV inputs on the DLATR6(8) rear panel or FT12-
TP and verify the absence of any resistance below 20M Ω between these inputs (cable on the front panel or
plug still connected to the detector). Verify that all cables are connected by identifying with an Ω meter the four
(six) pairs of contacts that connect to the ends of each wire on the connection cable to the feedthrough.
ƒ
Have amplifiers been damaged due to prior incidents of discharge, power failure, etc.?
ƒ Make sure that all the cables on the DLATR boards inside the (N)DLATR6(8) are connected (you need to
power down and open the box for that). In case of ATR19 : Did you connect the right inputs (+/-)?
ƒ
Is the power source for the ( N)DLATR6 strong enough (sufficient current, correct voltage)?
b) some are missing, some other look ok.”
ƒ
Make sure that the potentials on “holder”, “signal” and “reference” on are correct.
ƒ Is there a wiring error? Remove “signal” and “reference” SHV inputs on the DLATR6(8) rear panel or FT12-
TP and verify the absence of any resistance below 20M Ω between these inputs (cable on the front panel or
plug still connected to the detector). Verify that all cables are connected by identifying with an Ω meter the four
(six) pairs of contacts that connect to the ends of each wire on the connection cable to the feedthrough.
ƒ Have amplifiers been damaged due to prior incidents of discharge, power failure, etc.?
ƒ
Make sure that all the cables on the DLATR boards inside the (N)DLATR6(8) are connected (you need to
power down and open the box for that). In case of ATR19 : Did you connect the right inputs (+/-)?
ƒ
Is the power source for the ( N)DLATR6 strong enough (sufficient current, correct voltage)?