Energy Resolution of a Parallel-Plate-Avalanche-Chamber

Kausteya Roy

Professors E. Norbeck and Y. Onel

Background: Overview of Particles

• Basic types: fermions and bosons• Fermions- particles of matter, half integral spins• Types of fermions

– Leptons, weakly interacting particles, ex: electron– Hadrons- made up of quarks, strongly interacting

particles, types such as baryons, mesons– Ex of baryons: protons, neutrons

• Bosons- particles of force, integral spins• Fit into the Standard Model theory

Background: Future of Particle Detection

• Standard Model accounts for three of the Four basic forces

• Electromagnetic- photon

• Weak Nuclear- W boson

• Strong Nuclear- gluon

• Gravitational force is unaccounted for

• Theorized-Higgs boson and Graviton

Background: General Principle of Electromagnetic particle detectors

• Incoming particle decays into charged leptons or baryons

• Detectable using magnetic fields F=qvB, where q= charge on particle

• Other types: decelerate through a Voltage, such that qV=(1/2)mv2, or for relativistic speeds qV=mc2γ

• PPAC is a type of proportional counter, which uses wires to conduct signals

Background: A Future Particle detector

• PPAC is a type of low pressure gas detector• Two parallel plates filled with low pressure gas and a relative

electric potential of 930 volts• Electrons enter chamber and generate shower of knocked off

electrons• Called electron “avalanche”• Since an individual electron has too small a charge to be measured,

an avalanche is required to measure charge• Avalanche moves in direction determined by Voltage, which

generates an electric field across plates

Background

Background: Electron Avalanche Formula

• General form of Townsend’s law

• N(α,x)= exp(α,kx) where a is the Townsend coefficient and x is the distance within the detector

• For electron diffusion within electric field

• W= (-4π/3)(e/mN)(E/P) S v^2/o(m)df dv/dv

Advantage of PPAC

• Resistant to Radiation

• Simple to use

• Signal termination expected to be quick

• Distinct pulses

• Easy to analyze electronically

• High GeV Detection

Purpose of Experiment

• Test for PPAC time resolution

• Time required for second PPAC to register signal-expected 50nsec

• Test for PPAC Energy Resolution

• Closeness of pulses in both PPACs

• Test of voltage gain-expected 30mV

Electronic Setup (Timing Resolution)

Discriminators Cable Delay TDC

Stop

Start

RadioactiveSource

PPAC Dual-Output Preamp

-750V

The Radioactive source emits Beta particles, which emulate a high energy hadron shower.

Electronic Setup (Energy Resolution)

RadioactiveSource

PPAC Dual-Output Preamp

ADC

ADC

SpectroscopyAmplifiers

-750V

Preliminary – Electronics Energy resolution

Data Collection: Useful Equations

• The equipment detects voltage, as well as time continuum for pulse

• Energy derivation

E= (1/R) t1St2 V(t) dt

R= Test Resistance, usually 50 ohms

Data: Timing Resolution

Avg Signal 15nsec

Data: Energy Resolution

Avg. Gain: 55mV

Data: Further Testing

• Testing at Fermi lab• 4 TeV proton beam• Further test-beams

with pions and mesons

• Pions- higher charge than electrons

• Mesons- quark, anti-quark pair

Conclusions

• Good Timing resolution-less than expected

• Preliminary photon testing shows good energy resolution

• Higher Voltage Gain than expected

Conclusions

• Data collection at 10kHz, given sufficiently fast support electronics

• Good frequency for current particle accelerators

Future Plans

• PPAC detector system

• Updated version of Stanford Linear Accelerator Center

• Use at CERN

Future Plans

• Multi-pixelated PPAC

Special Thanks To:

• Professor Yasar Onel

• Professor Edwin Norbeck

• Jonathan Olson

• All SSTP staff and students

• Will Swain

• Fermi National Accelerator Laboratory