The document summarizes a student's project to construct a voltage distribution circuit to allow a photomultiplier tube to detect cosmic rays. It describes how cosmic rays interact with the atmosphere, how scintillators convert particle interactions to photons, and how photomultiplier tubes work. It outlines the design and construction process for the circuit, including selecting components, soldering wires, testing, and troubleshooting issues. The student was ultimately able to see pulses from a scintillator indicating detection of cosmic rays and radioactive decays.

1. Cosmic Ray Research
BY: MATTHEW LETTERMAN
LOCK HAVEN UNIVERSITY – SENIOR TRADITIONAL PHYSICS MAJOR
ADVISOR: DR. JOHN REID
28 MARCH 2015
CPS-AAPT, MESSIAH COLLEGE

2. Richie LaSalle, Mackenzie Maurer, Logan Tate, Warren McDonald,
Cody Schrek, George McKinney

3. Outline
Introduction
Construction of a Voltage
Distribution Circuit
Conclusions
Future work

4. Introduction
 What are cosmic rays?
 Particles from a source outside of
earth
 Interact with the atmosphere
 Create particle showers
What can happen in showers?
(ionize, collide)
What makes it to the ground?
[muons]

5. Outline
Introduction
Construction of a Voltage
Distribution Circuit
Conclusions
Future work

6. How do we get the photomultiplier tube to see
cosmic rays?
 The photomultiplier tube (PMT) needs photons
to make an electrical signal
 Scintillators
 Two types we use – Organic (hydrocarbons) and
Inorganic (NaI)
 Scintillators work by ionization – ionize all along
path of particle
 Particle gives energy through ionization or collision
 Ionized electrons lose energy through vibrations

7. Photomultiplier Tubes
 How do photomultiplier tubes work?
 Use the photoelectric effect
 Electrons knocked off photocathode by
incident photon
 Electric field moves electrons
 Move from dynode to dynode
 PhotonsElectronsElectrical Signal

8. Photomultiplier Tube Circuits
 Each resistor will experience a
voltage difference
 Each dynode will have a different
voltage allowing for electrons to
move
1000 Volts
500 Volts400 Volts200 Volts50 Volts0 Volts

9. Photomultiplier Tube Base
 The base connects to the external pins
of the photomultiplier tube
 The base has a socket
 Each pin has a different electrical input
 A case is used to protect the electronics
 Different shapes and sizes
 A voltage distribution circuit – apply
different voltage to dynodes

10. Why build and not buy?
 Cost
 It’s not the destination, it’s
the journey!
Description Quantity Price per unit ($) Total Cost of Units ($)
Resistors 13 0.09 1.17
Capacitors 3 0.91 2.73
SHV connectors 1 15.76 15.76
Solder wick 1 3.01 3.01
BNC Connectors 2 3.15 6.30
Circuit board 1 2.49 2.49
Total Cost ($) 31.46

11. Where do we start?
 First looked at the photomultiplier tubes used for
Landau tests
 Used the P30CW5 built by Sens-Tech
 Looked at the specifications and narrowed down
the ones that mattered
 Photocathode spectral response, photocathode
type, photocathode active diameter, spectral
response range, output pulse, output pulse time,
and max input
 These were the guidelines to be followed for
purchasing a new photomultiplier tube

12. Hamamatsu
 Picked the R1924A
 Purchased two R1924A

13. The Base Begins
 Begin with understanding
circuit from Hamamatsu
 Figure out the values for
each resistor and capacitor
 Find all the parts needed
and make a list
1000 V
500 V
400 V200 V50 V
0 V

15. Design of Circuit
 Sketch: This helped to determine how
and where parts were to be soldered
 Board Assembly: This was done to see
how much space was needed for the
board
 Back Side: Made hooks for wires to be
attached

16. Wires Soldered to Hooks
 Wires were then soldered
to the hooks
 This made it easier to
replace or fix wires
 This was in preparation for
the wires to be soldered to
the socket
First to
Last on
Circuit
Pin # Wire #
1 1 1
2 2 2
3 14 12
4 3 3
5 13 11
6 4 4
7 12 10
8 5 5
9 11 9
10 6 6
11 10 8
12 7 7

17. Case Designs
 Cylindrical Design
 Box Design
 Bar Design
 Criteria:
 Light-weight
 Removable Cover
 Modifiable
 Readily Available Parts
 Time Constraints

18. Recycled Parts
 Used a cylindrical design that was used
with another photomultiplier tube
 Was done to save time and money (not
feasible in our time frame)
 Few Problems:
 There was nowhere to attach the board to
the rails
 The hole was too big for the socket
 Board is too big

19. Fixing Problems
 Advisor did work to fix the problems
 Cut a new circular plate to attach the
socket to
 Cut the board to make it small enough
to fit into the enclosure
 Drilled/Tapped holes into the rails to
attach the board

23. Attach wires to socket
 The socket still needed to be
wired to the circuit
 This step was tedious and fragile
 Did not want to melt the plastic of
the socket
 After the wires were attached,
some minor testing was
conducted

24. Initial Test
 Low voltage test
 To make sure each pin
on the socket has the
right output
Pin # Voltage
(Volts)
Dynode
Number
Voltage
(Volts)
1 19.29 K 19.29
2 13.82 1 13.82
3 10.81 2 12.28
4 8.08 3 10.81
5 5.45 4 9.42
6 2.839 5 8.08
7 0 6 6.76
8 0 7 5.45
9 0 8 4.15
10 1.447 9 2.839
11 4.15 10 1.447
12 6.76 P 0
13 9.42
14 12.28

25. Black Box Test
 Photomultiplier tube placed against
inorganic scintillator with optical
grease
 Used High Voltage negative power
supply
 Oscilloscope used to see output
 High voltage pushed to 1,200 volts
and no pulses were seen

26. Back to the drawing board
 Redesigned circuit to allow for a
high positive voltage input instead
of high negative voltage
 Two resistors and two capacitors
were added to the circuit
 One resistor and capacitor were the
same values as the rest of the circuit
 One new resistor had a large value
 One capacitor had a small value

27. Test 2
 Another test was done and
yet no pulses were seen
 With voltage raised up to
1,000 volts there were still
no pulses
 This made no sense and we
could not understand why

28. Troubleshooting
 My advisor built a
prototype circuit on a
breadboard to help find
problems
 He used the black box and
saw pulses
 I then studied this
breadboard and we
discovered wiring mistakes
in the soldered circuit

29. Results at Last
 After making the minor fixes, I was able to
see a pulse from the inorganic scintillator
 Cs – 137 Pulses
 Cosmic Rays

30. Conclusions
Successfully designed and
built a photomultiplier tube
base

31. Future Work
 Put circuit in a better enclosure
 Build the 2nd base for the other
photomultiplier tube
 Refining system – ringing
10 ns / div100 ms / div