X-ray Polarimetry with gas proportional counters through rise-time

X-ray Polarimetry with gas proX-ray Polarimetry with gas proportional counters through riseportional counters through rise

-time-time

K. Hayashida, T. Horikawa, K. Hayashida, T. Horikawa, 　　 Y. Nakashima, Y. Nakashima, H. Tsunemi H. Tsunemi

(Osaka University, Japan)(Osaka University, Japan)

Acknowledge toAcknowledge toY. Namito (KEK, Japan) Y. Namito (KEK, Japan)

N.Tokanai (Yamagata Univ, Japan)N.Tokanai (Yamagata Univ, Japan)B.Paul (TIFR, India)B.Paul (TIFR, India)

X-ray Polarimeters in AstronomX-ray Polarimeters in Astronomyy

Bragg Crystal ReflectionBragg Crystal Reflection OSO8,ArielV satellites (1970’s) OSO8,ArielV satellites (1970’s)

Compton ScatteringCompton Scattering Planned for Spectrum X-Gamma mission (1990’s)Planned for Spectrum X-Gamma mission (1990’s)

Tracking Photo-electron Emission DirectionTracking Photo-electron Emission Direction X-ray CCD (Tsunemi et al., 1992)X-ray CCD (Tsunemi et al., 1992) Micro electrodes Gas Chambers (Costa et al., 2001; Micro electrodes Gas Chambers (Costa et al., 2001;

Tanimori et al., 1999; Sakurai et al., 1996)Tanimori et al., 1999; Sakurai et al., 1996)

Observations have been almost stagnant since 1970’s for more than 20 years.

Rise Time PolarimeterRise Time Polarimeterusing Gas Proportional Counter using Gas Proportional Counter

Proposed by Riegler et al., Sanford et al., in 1970.Proposed by Riegler et al., Sanford et al., in 1970. We re-examined the method. (Hayashida et al., 1999, NIWe re-examined the method. (Hayashida et al., 1999, NI

MA, 421,p.241) MA, 421,p.241)

Anode

Electron Cloud

E��

Rise Time = Short Rise Time = Long

// E��

Anode Anode E��

X-ray Photon

Working principle

Experiment at Synchrotron Experiment at Synchrotron Facility (1992-1993)Facility (1992-1993)

Anode Direction

Electric Vector // Vertical Direction

Double Crystal Spectrometer

BL14CVacuum Air

Pb Shield

2mmHole

Vertical Wiggler

SOR

Xe Gas Proportional Counter

Ex=10-40keV (PEx=10-40keV (Pbeambeam~0.8; measured)~0.8; measured) Xe proportional counter = Ginga ASM backupXe proportional counter = Ginga ASM backup

Xe:736mmHg + COXe:736mmHg + CO22:25mmHg:25mmHg Multi cell type; 5cm depth, 5cmx30cm for each cellMulti cell type; 5cm depth, 5cmx30cm for each cell Anode 50Anode 50m Be; HV=1950Vm Be; HV=1950V

Irradiate position =12 mm from anode

2mm

(Hayashida et al., 1999, NIMA, 421,p.241)(Hayashida et al., 1999, NIMA, 421,p.241)

Rise Time MeasurementRise Time Measurement

0

20

40

60

80

100

-2.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0

Dig

itize

d V

olta

ge

(m

V)

Time(microsec)

E=40keV

PH

80% of PH

20% of PH

RT

Xe Gas Proportional Counter

Pre-AmplifierDigital Storage Oscilloscope

Shaping Amp Scaler

GPIB

Personal Computer

Sampling the output pulse from CSPA with Sampling the output pulse from CSPA with Digitized Oscilloscope.Digitized Oscilloscope.

RT and PH are determined from the waveform RT and PH are determined from the waveform data transferred to the computerdata transferred to the computer

Results (Ex=34keV)Results (Ex=34keV)

0

20

40

60

80

100

120

140

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

34 keV =0deg.

Num

ber

of

events

risetime(microsec)

0

20

40

60

80

100

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

34keV Q=90deg.

Num

ber

of

events

risetime(microsec)

0

20

40

60

80

100

120

140

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

34keV Q=180deg.

Num

ber

of

events

risetime(microsec)

0

20

40

60

80

100

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

34keV Q=270deg

Num

ber

of

events

risetime(microsec)

0.40

0.45

0.50

0.55

0.60

0 90 180 270(deg)

34 keV

rise

tim

e (

mic

rose

c)

RT distribution <RT> vs


X-ray Energy X-ray Energy dependencedependence

0.40

0.45

0.50

0.55

0.60

0 30 60 90

rise

time

(mic

rose

c)

(deg)

10keV

0.40

0.45

0.50

0.55

0.60

0 30 60 90

rise

tim

e(m

icro

sec)

Q (deg)

20keV

0.40

0.45

0.50

0.55

0.60

0 30 60 90

rise

tim

e(m

icro

sec)

Q (deg)

30keV

0.40

0.45

0.50

0.55

0.60

0 30 60 90

rise

time

(mic

rose

c)

(deg)

34keV

0.40

0.45

0.50

0.55

0.60

0 30 60 90

rise

tim

e(m

icro

sec)

Q (deg)

36keV

0.40

0.45

0.50

0.55

0.60

0 30 60 90

rise

tim

e(m

icro

sec)

Q (deg)

40keV

Large modulation & lonLarge modulation & longer RT at higher energyger RT at higher energy

Note: Xe-K edge =34.6Note: Xe-K edge =34.6keV keV Events were selected usiEvents were selected usi

ng PH. ng PH. RT cutoff of 1RT cutoff of 1s is emplos is emplo

yed.yed. Most of the eMost of the events with vents with

K-fluorescent were likely K-fluorescent were likely to be excluded.to be excluded.


Modulation Factor MModulation Factor M

0.0

0.1

0.2

0.3

0.4

0.5

0 10 20 30 40 50

Mo

du

lati

on

Co

ntr

ast

Inciden X-ray Energy (keV)

2 2

90 0

2

90 0 / 2

: STD of RT distribution

RT beam

RT RTRT

RT

RT RTM

P

min

Minimum Detectable Polariza

c

ti

f

on (MDP)

event

aP

M N

M


Figure of merit for polarimter, larger the better.

Extra Experiment for VerificationExtra Experiment for Verification

0.40

0.45

0.50

0.55

0.60

0 30 60 90

(deg)

36keV Polarized

rise

tim

e(m

icro

sec)

0.40

0.45

0.50

0.55

0.60

0 30 60 90Q (deg)

Sn K a (25.2 keV)ri

seti

me(m

icro

sec)

0.40

0.45

0.50

0.55

0.60

0 30 60 90Q (deg)

Sn K b (28.5 keV)

rise

tim

e(m

icro

sec)

Thin Sn filter was placed at the beam exit, whicThin Sn filter was placed at the beam exit, which produced Sn Kh produced Sn K,K,K fluorescent X-rays in additi fluorescent X-rays in addition to polarized 36 keV X-rays. on to polarized 36 keV X-rays.


Feasibility Study PC polarimeter Feasibility Study PC polarimeter Merit of the PC rise time polarimeterMerit of the PC rise time polarimeter

Only need to add RT processing unit to conventional PCcOnly need to add RT processing unit to conventional PCc Large effective area is easily realized without mirrors.Large effective area is easily realized without mirrors.

T=20ks

Balloon Observation

A pair of 300cm2 PCs will provide Polarization degrees (if P>5%) for each 5keV band.

0

5

10

15

20

10 20 30 40 50 60 70

Minimum Detectable Polarization

Pmin(%) 1200cm2/counterPmin(%) 300cm2/counter

Ex(keV)

99% confidence levelfor each 5keV band

Polarized X-ray Beam Line at OsakaPolarized X-ray Beam Line at Osaka

Measurement Chamber

Double Crystal Monochrometer

Electron Impact type X-ray Generator

Monochromatic beam with linear polarization degree of 40-50% is obtained. (Koike et al., 2000, SPIE4012, p.414)

Bremstrahlung X-rays are partially polarized.

Pickup X-rays whose energy (Ex keV) is close to applied High Voltage (HV kV)

Experiment at Osaka Beam Line Experiment at Osaka Beam Line (2001-2002)(2001-2002)

Two kinds of Gas PCsTwo kinds of Gas PCs Ar gas flow type PCAr gas flow type PC

Wire 50Wire 50mm Quenching gas (CH4) of Quenching gas (CH4) of

various contents were exvarious contents were examined.amined.

Xe gas shield type PC (tXe gas shield type PC (the same one used in Syhe same one used in Synchrotron Facility)nchrotron Facility)

Data taking system waData taking system was upgraded. s upgraded.

X-ray

X-ray

E90,270

0,180

angle

RT vs angle

2.45

2.5

2.55

2.6

2.65

2.7

- 90 0 90 180 270 360 450[degree]

RT[

usec

]

0.2700.2650.260

0.2500.255

0.245

However, Results are …However, Results are …M vs E

-0.05

0

0.05

0.1

0.15

25 30 35 40 45 50E[keV]

M

Gas Content　　 Xe96.7%+CO23.3%　　 Ar 90% +CH410%　　 Ar99.3%+CH40.7%

Contents of Quenching Gas is very sensitive to RT. Contents of Quenching Gas is very sensitive to RT. Ar 99.3% +CHAr 99.3% +CH44 0.7% provided M of 0.05-0.1. 0.7% provided M of 0.05-0.1. Small!Small! More seriously, the same Xe counter used in 1992-1993 yielMore seriously, the same Xe counter used in 1992-1993 yiel

ded M of less than 0.05. ded M of less than 0.05. Discrepancy!Discrepancy!

Incident position

12mm from anode for Xe PC

10mm from anode for Ar PC

Preliminary Simulation using Preliminary Simulation using EGS4EGS4

Ar-Gas P=1atm Ex=20keV Ar-Gas P=1atm Ex=50keV

EGS4 (Electron Gamma Shower Simulator ver4) + KEK low EGS4 (Electron Gamma Shower Simulator ver4) + KEK low energy extensionsenergy extensions

Energy deposit and path of photoelectrons are simulated.Energy deposit and path of photoelectrons are simulated. Large effect of multiple scattering is observed. Large effect of multiple scattering is observed.

10mm1mm

E

M expected from EGS4 SimulationM expected from EGS4 Simulation

0

0.1

0.2

20 30 40 50

M (Ne) M (Ar) M (Xe)

Ex(keV)

0.01

0.1

1

20 30 40 50

Ne _|_(cm)

Ne //(cm)

Ar _|_(cm)

Ar //(cm)

Xe _|_ (cm)

Xe // (cm)

Ex(keV)

Dispersion of the distance to anode () cm M

2

for each photo-absorption event

/

( ) /

i i i

i i i

d E d E

E d d E

•Small energy dependence

•M=0.03-0.06 for Ar, <0.03 for Xe

•NOTE: gas processes (diffusion, avalanche etc) is not considered.

*) If multiple scattering does not exist, M would be 0.78.

M

Siz

e

(cm

)

time

PMT Out

time

PMT Out

0˚ case

90 ˚ case

Electric Vector

PMT

Electron Cloud

Gas Amplification

Capillary Plate

Capillary Plate Gas Chamber

Xrays(90˚)

Xrays(0˚)Xray Detection Layer

Quartz

Pulse width is measuredSaito et al, 2001

CPGC with Ar gas provided M=21% ＠ 20keV in an experiment at Osaka Beam LineEGS4 simulation predicts M=5%How valid the EGS4 simulation (multiple scattering) is in the low energy end ?

What causes the discrepancy ?What causes the discrepancy ? Strong dependence of X-ray Strong dependence of X-ray

incident position on RT was incident position on RT was observed.observed.

Misalignment of rotation axis Misalignment of rotation axis could have made an artifact could have made an artifact modulation.modulation.

But,But, the modulation should h the modulation should have 1 peak / 360ave 1 peak / 360˚̊, not like o, not like observed 2 peaks / 360bserved 2 peaks / 360˚̊..

Sn-filter result was not explaSn-filter result was not explained by the misalignment, eitined by the misalignment, either.her.

0.40

0.45

0.50

0.55

0.60

0 90 180 270(deg)

34 keV

rise

tim

e (m

icro

sec)

Anode

12mmExperiment at Synchrotron Facility is planed in this Nov.

SummarySummary

Gas proportional counter polarimeter with rise tiGas proportional counter polarimeter with rise time measurement is introduced. me measurement is introduced.

Previous experiment at Synchrotron facility proviPrevious experiment at Synchrotron facility provided M of 0.1-0.3 with Xe PC, while recent experided M of 0.1-0.3 with Xe PC, while recent experiment (Xe PC, Ar PC) provides much smaller M.ment (Xe PC, Ar PC) provides much smaller M.

Preliminary simulation also suggests M <0.1 It alPreliminary simulation also suggests M <0.1 It also contradicts the CPGC result of M=0.2.so contradicts the CPGC result of M=0.2.

No firm solution has not yet been obtained for thNo firm solution has not yet been obtained for the discrepancy. e discrepancy. Sorry for inconclusive, confusing Sorry for inconclusive, confusing results.results.

X-ray Polarimetry with gas proportional counters through rise-time

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