Development of a Development of a Gamma-Ray Beam Gamma-Ray Beam

Profile Monitor for the Profile Monitor for the High-Intensity Gamma-High-Intensity Gamma-

Ray SourceRay Source

Thomas Regier,Thomas Regier,Department of Physics and Department of Physics and

Engineering PhysicsEngineering PhysicsUniversity of Saskatchewan University of Saskatchewan

Beam Profile MonitorBeam Profile Monitor

Component of Beam Component of Beam Diagnostic SystemDiagnostic System

Provides Gamma-Ray Provides Gamma-Ray Position and Flux Position and Flux InformationInformation

Assists users and Assists users and operators in operators in experiment and beam experiment and beam configurationconfiguration

The High Intensity Gamma-Ray The High Intensity Gamma-Ray SourceSource

270 MeV Linear Accelerator

Electron Source

Electron Storage Ring

OK-5 Free Electron Laser

RF Booster

Experimental Area

Design RequirementsDesign Requirements

Sub-millimeter resolutionSub-millimeter resolution

Easy to useEasy to use

Non-destructiveNon-destructive

Handle beam energies between 2 and 225 Handle beam energies between 2 and 225 MeVMeV

Handle beam fluxes between 10Handle beam fluxes between 105 5 and 10and 101010 gammas per secondgammas per second

Detecting Gamma-RaysDetecting Gamma-Rays

Design ConceptDesign Concept

Gamma-Rays interact with the scintillator, generating flourescent illumination.

The illuminated scintillator is imaged onto a Charge Coupled Device by a lens system.

The CCD records the illumination pattern by converting the incident photons into electrons

System ModelSystem Model

NC

Relates the number of counts registered by the CCD camera to the power absorbed by the scintillator and the length of the exposure through the

responsivity of the system.

RSYS Pabsorbed tINT= int[ ]

CCD NoiseCCD Noise

DesignDesign

Light Tight Box

CCD Camera

Lens System

Scintillator

Inrun / Outrun Windows

CCD CameraCCD Camera

Starlight Express MX-5Starlight Express MX-5 Sony ICX055BL CCD ChipSony ICX055BL CCD Chip Single Stage Thermoelectric Single Stage Thermoelectric

Cooler (Room Temp – 30Cooler (Room Temp – 30ooC)C) External USB ControllerExternal USB Controller Capable of ‘binning’Capable of ‘binning’

Linux Based Data AcquisitionLinux Based Data Acquisition 33rdrd Party USB drivers Party USB drivers Custom camera control Custom camera control

softwaresoftware

OpticsOptics

- Had to balance…Had to balance…- Overall lengthOverall length- Number of lensesNumber of lenses- ApertureAperture- MagnificationMagnification

Source TestingSource Testing- Used 23 mCi 137Cs source to test system response

- Testing resulted in a series of improvements to apparatus

137137Cs Emission SpectrumCs Emission Spectrum

Data Analysis/ProcessingData Analysis/Processing

Original Image of 137Cs Source Radiation

Background Subtracted Image

Image processed to remove bad pixels

CalibrationCalibration

-Performed to find the system responsivity, RSYS

-Combines…

- Source profile measurement data

- Source flux measurement data

- Geant simulation results

-Provides a link between the image intensity and the gamma-ray flux

Source Profile Data

Geant Simulation

Source FluxMeasurement

-Determined by the number of counts in a particular region of the image, divided by the amount of energy deposited in the corresponding region on the scintillator

RSYS = NC / (Pabsorbed tINT) = 126 Counts per GeV

Source Flux Measurement with NaI

Detector

and

Geant Simulation Results

Predicted Exposure TimesPredicted Exposure Times

-Dictated by the signal to noise ratio

-Calculated by examining an individual camera “bin”

Portion of the signal generated by something other than the incident

illumination

Portion of the output signal generated due to exposure to illumination

nfull

rsysPabsorbedtINTnT = + idarktINT + nfloor

Predicted Exposure TimesPredicted Exposure Times

nT = rsysPabsorbedtINT + idarktINT + nfloor

nB = idarktINT + nfloor

nS = nT – nD = rsysPabsorbedtINT

δnS2 = δnT

2 + δnB2

Background Subtraction is performed to find signal

Predicted Exposure TimesPredicted Exposure Times-Select a fraction of error, ε, that gives

εnS(tINT) = δnS(tINT)

-Find a solution for tINT that satisfies this relationship

A Plot of the Time Required to Obtain a Fraction of Error, ε, for Pabsorbed Values of 20, 60 and 100 GeV/s

ε

The Time Required to Achieve 5% Error Per Pixel Versus Beam Energy For Various Scintillator-Converter Configurations

ConclusionsConclusions

- The combination of a scintillator, lens system, and CCD camera can be used to measure the profile of a gamma-ray source

- Submillimeter resolutions are achievable

- The method is non-destructive

- Predicted exposure times for a nominal beam flux are less than a minute

In-Beam TestingIn-Beam Testing

In-Beam TestingIn-Beam Testing

In-Beam TestingIn-Beam Testing

In-Beam TestingIn-Beam Testing

In-Beam TestingIn-Beam Testing

In-Beam TestingIn-Beam Testing

In-Beam TestingIn-Beam Testing

In-Beam TestingIn-Beam Testing

In-Beam TestingIn-Beam Testing

In-Beam TestingIn-Beam Testing