Measurementof Gas Bremsstrahlung

at the Pohang Light Source

Hyosang LeeSeoul National University, Q2C

Pusan National University, HANUL

HNP2011

Contents

Measurement of gas bremsstrahlung

Measurement of hadron photoproduction

MotivationPohang Light Source (PLS)

3rd generation synchrotron facility with a beam emittance of 18.9nm⋅rad

2.5GeV electron linear accelerator : full energy injector for the storage ring

2.5GeV Electron Storage Ring: 12-period Triple Bend Achromat lattice

180mA at 2.5GeV

Design to provide synchrotron radiation with continuous wavelengths down to 1Å

LINAC

Storage Ring

MotivationBremsstrahlung

produced through electromagnetic interactions of circulating electrons

with storage ring components

with residual gas in vacuum

carrying polarization information of the electrons circulating

time evolution of the electron polarization(due to spin-flip synchrotron radiation) -> electron energy

measurement of gas bremsstrahlung = measurement of electron energy

Eγ = 0 ∼ Emax,e-

First gas bremsstrahlung measurement at PLS

Experimental method3 data taking run : 2007, 2009, 2010

Detector : scintillation crystal [CeF3, PbWO4, CsI]

1C1 beam line

straight section with 5.3 m

vacuum : 0.5nTorr

photon transport : 6.3ϕ, 13.6m

soft-X ray shielding : 2mm Pb slabs

componentcomponent Mole fraction(%)Mole fraction(%) Weight fraction(%)Weight fraction(%)

H2 90 41.86

N2/CO 5 32.55

CH4 3 11.16

CO2 1 10.23

H2O 1 4.18

Experimental method

CeF3

PbWO4CsI

Detector : CeF3, PbWO4, CsI

Tungsten collimator : ϕ3, 7mm

veto by plastic scinti. to reject e+e-

Beam profile - 2007 data

tungsten wire + 1x1mm2 scinti.

CeF3

x-axis : 10mm

y-axis : 4mm

Raw data & Energy Calibrationcenter CeF3 : ~78% (MC 77.6%)

1/Eγ distribution

Geant4 simulation center - 77.6% surrounding - 19.4% leakage - 3%

Energy calibration

Result - 2007 data

photon flux - 10/s @ >400MeV with 180mA - 39/s @ 180mA

Energy resolution -

Experimental setup - 2009

Detector PbWO4 : 1.9cm x 1.9cm x 20cm CsI : 7cm x 7cm x 30cm

5B1 beam line with 5.3 m straight line

PWO centerPWO sumTotal sumCeF3 sum

Result - 2009

Result - 2009

Need energy calibration with fixed energy beam

CsI energy

PWO energy

Energy sum

??

Hadron photoproduction - motivation

Hadron photoproduction : 0.23 Hz

By using gas bremsstrahlung

γp -> π0p

πp

Hadron photoproduction - Experiment3x3 PWO

5x5 CsITarget & Start Count

to measurebremsstrahlu

ng

to measureπ0->γγ

Measurement of bremsstrahlung

Measurement of hadron photoproduction with γp->π0p

Experimental setup

start time

ToFto measure p

Beam

γp -> π0p

Hadron photoproduction - SignalUpveto Start Counter

Multiplicity in ToF ToF

Hadron photoproduction - ToF Calibration

t0 calibration

time correction

position calculation

Hadron photoproduction - CsI Calibration

CsI calibration with cosmic-ray muon

Hadron photoproduction - γ clustering

Geant4 simulationreal data

clustering method

No π0 events ?

Next to do : - γ hit position - energy leakage - energy calibration

No π0 events ?

Next to do : - γ hit position - energy leakage - energy calibration

Hadron photoproduction - π0 mass

real data

Geant4 simulationCeF3 Energy

Hadron photoproduction - Dipole Magnet

Hadron photoproduction - Dipole Magnet

SummaryMeasurement of Gas Bremsstrahlung

First measurement

3 data run

Detector : CeF3, PbWO4, CsI

photon flux - 10/s @ >400MeV with 180mA - 39/s @ 180mA

Need to energy calibration with fixed energy beam

Measurement of Hadron

Hadron photoproduction : 0.23 Hz

By using gas bremsstrahlung

γp -> π0p