Cosmic Ray ResearchBY: MATTHEW LETTERMANLOCK HAVEN UNIVERSITY – SENIOR TRADITIONAL PHYSICS MAJORADVISOR: DR. JOHN REID28 MARCH 2015CPS-AAPT, MESSIAH COLLEGE

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

Outline

IntroductionConstruction of a Voltage

Distribution CircuitConclusions Future work

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]

Outline

IntroductionConstruction of a Voltage

Distribution CircuitConclusions Future work

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

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 PhotonsElectronsElectrical Signal

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

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

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

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

Hamamatsu

Picked the R1924A Purchased two R1924A

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 V400 V200

V50 V

0 V

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

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

Circui

t

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

Case Designs

Cylindrical Design Box Design Bar Design Criteria:

Light-weight Removable Cover Modifiable Readily Available Parts

Time Constraints

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

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

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

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

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

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

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

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

Results at Last After making the minor fixes, I was

able to see a pulse from the inorganic scintillator Cs – 137 Pulses Cosmic Rays

Conclusions

Successfully designed and built a photomultiplier tube base

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