The document summarizes the electronics used for the DRIFT dark matter detector. It describes how the detector uses carbon disulfide gas and wires to detect dark matter interactions. The original electronics design grouped wires together, increasing noise. A new multiplexing system was developed using Brookhaven National Laboratory integrated chips to read out individual wires. This reduced noise from 3500 electrons to 600 electrons. Additional boards and the full detector system achieve a total noise of 750 electrons.

1. Electronics for the
DRIFT Detector
Kevin Kuwata
Dr. Jean-Luc Gauvreau & Dr. Dan Snowden-Ifft
July 31, 2013

2. What is Dark Matter?
Matter in the Universe
15%
85%
Dark Matter Matter

3. What is Dark Matter?
• Does not interact through electromagnetic
radiation
• Does interact with gravity
• Theory points towards weak force

4. DRIFT
Carbon disulfide (CS2)

5. DRIFT
CS2
-
CS2
Cathode
Wires

6. Current Design:
Pre-Amp Shaper Digitizer
Detector
Wire

7. Current Design Cost
• Pre-Amp: CR110
• $155.00
• Shaper: CR200
• $ 155.00
• Digitizer:
• $500
• Per Wire Total: $810 per channel

8. Grouping Wires
1
2
3
4
5
6
7
8
9
10
11
12
Ch. 1
Ch. 2
Ch. 3
Ch. 4
...
...
...
...

9. Problems:
• Grouping increases capacitance, due to
large number of wires hooked up to each
channel, which increases the noise to an
unacceptable level
• No information about location of event

10. Grouping Wires
1
2
3
4
5
6
7
8
9
10
11
12
Ch. 1
Ch. 2
Ch. 3
Ch. 4
...
...
...
...

11. Solution: Multiplex
Selection
• Reduce the noise by ungrouping
• Requires inexpensive electronics

12. Brookhaven National
Laboratory (BNL)
• Replaces Pre-Amplifier and Shaper
• Developed the integrated chip (IC) that
allows the detector to be sensitive to
quantities of charge.
• 16 wires per BNL Chip
• $100 per wire previously, down to $5 per
wire

13. BNL Board
Input
Output Output
BNLControl

14. BNL details
• Gain
• Peak time
• AC coupling
• Test signal

15. Programming the BNL
Board: Arduino
Control Board
• The BNL board can be programmed by
sending a series of pulses
• LabJack® initially programming BNL board,
now using Arduino Mega2560

16. Multiplexing
• Multiplexing: process of taking selecting one
of several signals
• Allows for the individual wire testing

17. Multiplexer
Output
Inputs

18. Multiplexer:Address
• The “Address” of the multiplexer can be
thought as a street address of a house
Output
Inputs
S0
S1

19. Address Selection
• S0 and S1 determine the address. S0 and S1
are binary (1,0)
(0,0) (0,1)
(1,0) (1,1)
Output
= 0
0
= 1
1
= 2
2
= 3
3

20. Address Selection
• (S0, S1)
(0,0) (0,1)
(1,0) (1,1)
2
1 3
0
Output

21. Multiplexing Wires
1
2
3
4
5
6
7
8
9
10
11
12
Ch. 1
Ch. 2
...
...
...
...
...
Output

22. Multiplexing Board
• Multiplexing board uses 17, 8-channel
multiplexing integrated circuits to select 1
wire out of a 120.

23. Multiplexing Board

24. Multiplexing Board
Output
Input

25. Measurements

26. Height Measurements
Max Height
MaxHeight(Volts)
0.00
0.75
1.50
2.25
3.00
Channel
0.0 12.2 24.4 36.6 48.8 61.0 73.2 85.4 97.6 109.8 122.0
• σ = ± 2 %
• x̅ = 2.46V ± .05

27. Height Measurements
Max Height
Voltage(V)
2.3500
2.3875
2.4250
2.4625
2.5000
Wire
0.0 12.2 24.4 36.6 48.8 61.0 73.2 85.4 97.6 109.8 122.0

28. Width @ 50% Height
Measurements
• σ = ± 2%
• x̅ = 2.48 ±.05 µS
Width
Width(µS)
0.00
0.65
1.30
1.95
2.60
Channel
0 12 24 36 48 60 72 84 96 108 120

29. Width @ 50% Height
Width
Width(µS)
2.38
2.43
2.49
2.54
2.60
Channel
0 12 24 36 48 60 72 84 96 108 120

30. Noise Measurements
• noise 3500 electrons, grouping
• noise bnl 600 electrons
• 600 electrons noise after Multiplexer
Board
• Boards & Detector Total noise: 750
electron
• ~1 trillion (10^12) electrons in static shock
electrons in
static disch

31. Supplementary Slides

32. Supplementary Slide:
Address Selection
• S0 and S1 determine the address. S0 and
S1can be either On (1) or Off (0).
(0,0) (0,1)
(1,0) (1,1)
0 1
0
1
Output
= 0
0
= 1
1
= 2
2
= 3
3

33. Supplementary Slide:
Address Selection
• S0 and S1 determine the address. S0 and
S1can be either On (1) or Off (0).
(0,0) (0,1)
(1,0) (1,1)
0 1
0
1
2
1 3
0
Output

34. Supplementary Slide:
Address Selection
• S0 and S1 determine the address. S0 and
S1can be either On (1) or Off (0).
(0,0) (0,1)
(1,0) (1,1)
0 1
0
1
2
1 3
0
Output

35. Supplementary Slide:

36. BNL Monitoring
• Arduino monitors “Status” line of the BNL
• Notifies user of a possible error in the
BNL parameters
• Automatically reset’s BNL boards if they
become un-programmed

37. BNL Monitoring
Is the
Status
OK?
No yes
Reset
> 1.0
Resets/
Minute?
No yes
Turn On
Indicator
Light

38. Multiplexing Wires
Ch. 1
1
9
17
Ch. 2
2
10
18
Ch. 3
8
16
24
Multiplexers (Mux)

39. In-Field Programming
• Ability to change settings away from
computer
• no technical programming required