Mark L. McConnell, James R. Ledoux, John R. Macri, Matt Orr, and James M. Ryan

Space Science CenterUniversity of New Hampshire

Durham, NH

X-Ray Polarimetry Workshop SLAC / Stanford 9-11 February 2004

GRAPEA Balloon-Borne

Gamma-Ray Polarimeter (50-300 keV)

GRAPE Science Model (SM1)Gamma-RAy Polarimeter Experiment

Scattering Elements• 280 element array of plastic

• each 5 mm square by 5 cm long • optically isolated

• read out by a 5-inch PSPMT• Hamamatsu R3292 PSMT

Calorimeter Elements• 4 element array of CsI(Tl)

• each 1cm square by 5 cm long• read out by a MAPMT

• Hamamatsu R5900 MAPMT

Position-Sensitive PMTHamamatsu R3292

Plastic ElementsBC-404

CsI(Tl)Array

On-Axis Performance

4

3

2

1

0

Effe

ctiv

e A

rea

(cm

2 )

3 4 5 6 7 8 9100

2 3 4 5

Energy (keV)

101.6 mm 88.9 mm 76.2 mm 63.5 mm 50.8 mm 25.4 mm

Effective Area vs. Depth

Simulations (based on a modified version of GEANT3) have been used to characterize the design.

On-Axis Performance

7

6

5

4

3

2

1

0

Figu

re o

f M

erit

(rel

ativ

e)

3 4 5 6 7 8 9100

2 3 4 5

Energy (keV)

76.2 mm 50.8 mm 25.4 mm 63.5 mm 88.9 mm 101.6 mm

Figure-of-Merit vs. DepthThe figure-of-merit

incorporates an estimate of the increased

background as a function of detector volume.

Optimum Depth for this design is ~3 inches

FoM =µ100 !A√

Vdet

Off-Axis Performance

1.0

0.8

0.6

0.4

0.2

0.0

Mod

ulat

ion

Fac

tor

706050403020100Angle (Degs)

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Effective A

rea (cm2)

Modulation Factor Effective Area

7.62 cm depth @ 200 keV

The GRAPE design offers significant response even at large off-axis angles.

This makes GRAPE an attractive design for polarization studies of transient sources

(Gamma-Ray Bursts).

Science Model ComponentsThis photo shows the 5-inch PSPMT, the array of

plastic scattering elements and the MAPMT/CsI assembly.

GRAPE SM1 Lab Set-Up(drawing not to scale)

Photons partially polarized by scattering off a plastic

scintillator.

0.8

0.6

0.4

0.2

0.0

Pola

rizat

ion

Frac

tion

18016014012010080604020Scatter Angle (degs)

60 keV 662 keV 1200 keV

PMT PSPMT

662 keV, unpolarized

288 keV, partially polarized

POLARIZER POLARIMETER

plastic

scintillator

array

CsI

array

MAPMT

137Cs

Also provides electronic tagging of each photon.

Correction of SM1 Data

140012001000

800600400200

0

Coun

ts

350300250200150100500

Azimuthal Scatter Angle (degs)

GRAPE - SM1

Polarized Data(corrected)

The response to anunpolarized beam is used to correct for geometric

effects.

1.41.21.00.80.60.40.20.0

Coun

ts

350300250200150100500

Azimuthal Scatter Angle (degs)

GRAPE - SM1

Unpolarized Data(normalized) 356 keV

140012001000

800600400200

0

Coun

ts

350300250200150100500

Azimuthal Scatter Angle (degs)

GRAPE - SM1

Polarized Data(raw data) 288 keV

SM1 Results at 0° Incidence

Runs taken with the incident beam having apolarization angle that differs by ~90°.

1000

800

600

400

200

0

Corre

cted

Cou

nts

360300240180120600Azimuthal Scatter Angle (degs)

GRAPE Science Model (SM1)0° Incidenceφ = 40° ± 2°

700

600

500

400

300

200

100

0Co

rrect

ed C

ount

s360300240180120600

Azimuthal Scatter Angle (degs)

GRAPE Science Model (SM1)0° Incidenceφ = 134° ± 3°

Polarization = 62 (±3)% Polarization = 73 (±6)%

SM1 Results at 30° Incidence

1400

1200

1000

800

600

400

200

0

Corre

cted

Cou

nts

350300250200150100500Azimuthal Scatter Angle (degs)

GRAPE Science Model (SM1)30° Incidence

∆φ = 0°

1200

1000

800

600

400

200

0Co

rrect

ed C

ount

s

350300250200150100500Azimuthal Scatter Angle (degs)

GRAPE Science Model (SM1)30° Incidence

∆φ = 90°

Runs taken with the incident beam having apolarization angle that differs by ~90°.

Polarization = 63 (±4)% Polarization = 73 (±7)%

GRB SensitivityWe have estimated the polarization sensitivity of a long-duration balloon payload consisting of a planar array of 36 GRAPE modules, covering less than 1 m2 of area.

Frequency based on BATSE 4B catalog.

Solar Flare SensitivityThe solar flare polarization sensitivity for various energy bands. These data assume a balloon-borne

array of 16 GRAPE modules.

30

25

20

15

10

5

0

Min

imum

Det

ecta

ble

Pola

rizat

ion

(%)

6005004003002001000Energy (keV)

X1-Class Flare

X10-Class Flare

GRAPE Science Model (SM2)Gamma-RAy Polarimeter Experiment

Single module with MAPMT and FEE electronics.

0 %Generating EPSF... 1 %Generating EPSF... 2 %Generating EPSF... 4 %Generating EPSF... 5 %Generating EPSF... 7 %Generating EPSF... 8 %Generating EPSF... 9 %Generating EPSF... 11 %Generating EPSF... 12 %Generating EPSF... 14 %Generating EPSF... 15 %Generating EPSF... 16 %Generating EPSF... 18 %Generating EPSF... 19 %Generating EPSF... 21 %Generating EPSF... 22 %Generating EPSF... 23 %Generating EPSF... 25 %Generating EPSF... 26 %Generating EPSF... 28 %Generating EPSF... 29 %Generating EPSF... 30 %Generating EPSF... 32 %Generating EPSF... 33 %Generating EPSF... 35 %Generating EPSF... 36 %Generating EPSF... 38 %Generating EPSF... 39 %Generating EPSF... 40 %Generating EPSF... 42 %Generating EPSF... 43 %Generating EPSF... 45 %Generating EPSF... 46 %Generating EPSF... 47 %Generating EPSF... 49 %Generating EPSF... 50 %Generating EPSF... 52 %Generating EPSF... 53 %Generating EPSF... 54 %Generating EPSF... 56 %Generating EPSF... 57 %Generating EPSF... 59 %Generating EPSF... 60 %Generating EPSF... 61 %Generating EPSF... 63 %Generating EPSF... 64 %Generating EPSF... 66 %Generating EPSF... 67 %Generating EPSF... 69 %Generating EPSF... 70 %Generating EPSF... 71 %Generating EPSF... 73 %Generating EPSF... 74 %Generating EPSF... 76 %Generating EPSF... 77 %Generating EPSF... 78 %Generating EPSF... 80 %Generating EPSF... 81 %Generating EPSF... 83 %Generating EPSF... 84 %Generating EPSF... 85 %Generating EPSF... 87 %Generating EPSF... 88 %Generating EPSF... 90 %Generating EPSF... 91 %Generating EPSF... 92 %Generating EPSF... 94 %Generating EPSF... 95 %Generating EPSF... 97 %Generating EPSF... 98 % Sheet #3 Layer #1 1 X: 138.49mm Y: 104.32mm X: 73.24mm Y: 91.15mm 73.44mm Group of 69 objects

flat-panel PMT

FEE

plasticelements

Calorimeter Elements• 4 element array of CsI(Tl)

• each 5-mm square by 5-cm long• read out by same flat-panel MAPMT

• Hamamatsu H8500 MAPMT

CsIScattering Elements • 60 element array of plastic

• each 5-mm square by 5-cm long • optically isolated

• read out by a flat-panel MAPMT• Hamamatsu H8500 MAPMT

SM2 Module Logic

inorganic scintillator(CsI or LaBr3, calorimeter)

flat panelMAPMT

front-end electronics

or

or

fromotherMAPMTs

ADCs

event builderpulse

heights& hit IDs

coincidence

sparseeventdata

gate

plastic scintillator bars(photon scattering)

TextTextTextText

The single MAPMT provides independent signals for both the

scattering and calorimeter elements.

Eliminates additional mass in front for

calorimeter readout.

Large Area Arrays

0 %Generating EPSF... 1 %Generating EPSF... 2 %Generating EPSF... 3 %Generating EPSF... 4 %Generating EPSF... 5 %Generating EPSF... 6 %Generating EPSF... 7 %Generating EPSF... 8 %Generating EPSF... 9 %Generating EPSF... 10 %Generating EPSF... 11 %Generating EPSF... 12 %Generating EPSF... 13 %Generating EPSF... 14 %Generating EPSF... 15 %Generating EPSF... 16 %Generating EPSF... 17 %Generating EPSF... 18 %Generating EPSF... 19 %Generating EPSF... 20 %Generating EPSF... 21 %Generating EPSF... 22 %Generating EPSF... 23 %Generating EPSF... 24 %Generating EPSF... 25 %Generating EPSF... 26 %Generating EPSF... 27 %Generating EPSF... 28 %Generating EPSF... 29 %Generating EPSF... 30 %Generating EPSF... 31 %Generating EPSF... 32 %Generating EPSF... 33 %Generating EPSF... 34 %Generating EPSF... 35 %Generating EPSF... 36 %Generating EPSF... 37 %Generating EPSF... 38 %Generating EPSF... 39 %Generating EPSF... 40 %Generating EPSF... 41 %Generating EPSF... 42 %Generating EPSF... 43 %Generating EPSF... 44 %Generating EPSF... 45 %Generating EPSF... 46 %Generating EPSF... 47 %Generating EPSF... 48 %Generating EPSF... 49 %Generating EPSF... 50 %Generating EPSF... 51 %Generating EPSF... 52 %Generating EPSF... 53 %Generating EPSF... 54 %Generating EPSF... 55 %Generating EPSF... 56 %Generating EPSF... 57 %Generating EPSF... 58 %Generating EPSF... 59 %Generating EPSF... 60 %Generating EPSF... 61 %Generating EPSF... 62 %Generating EPSF... 63 %Generating EPSF... 64 %Generating EPSF... 65 %Generating EPSF... 66 %Generating EPSF... 67 %Generating EPSF... 68 %Generating EPSF... 69 %Generating EPSF... 70 %Generating EPSF... 71 %Generating EPSF... 72 %Generating EPSF... 73 %Generating EPSF... 74 %Generating EPSF... 75 %Generating EPSF... 76 %Generating EPSF... 77 %Generating EPSF... 78 %Generating EPSF... 79 %Generating EPSF... 80 %Generating EPSF... 81 %Generating EPSF... 82 %Generating EPSF... 83 %Generating EPSF... 84 %Generating EPSF... 85 %Generating EPSF... 86 %Generating EPSF... 87 %Generating EPSF... 88 %Generating EPSF... 89 %Generating EPSF... 90 %Generating EPSF... 91 %Generating EPSF... 92 %Generating EPSF... 93 %Generating EPSF... 94 %Generating EPSF... 95 %Generating EPSF... 96 %Generating EPSF... 97 %Generating EPSF... 98 %Generating EPSF... 99 % Sheet #2 Layer #1 1 X: 138.49mm Y: 106.32mm X: 30.37mm Y: 78.62mm 154.33mm Group of 5 objects

Large area arrays can easily be fabricated.

Inter-module events will increase the effective area.

Large areas could be used as an imaging

detector plane.

Lab Testing of SM2 Module

The H8500 provides an 8 x 8 array of anodes on

a 6-mm pitch.

Now in Progress

SM1 vs. SM2 Array

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Effe

ctiv

e Ar

ea (c

m2 )

3 4 5 6 7100

2 3 4 5 6 71000

2

Energy (keV)

SM1 (PSPMT) SM2 (MAPMT)

Effective AreaSM1 vs. SM2 Array

1.0

0.8

0.6

0.4

0.2

0.0M

odul

atio

n Fa

ctor

(µ10

0)3 4 5 6 7

1002 3 4 5 6 7

10002

Energy (keV)

SM1 (PSPMT) SM2 (MAPMT)

Modulation FactorSM1 vs. SM2 Array

These simulation results compare a single SM1 module with a 4-element array of SM2 modules.

10

8

6

4

2

0

Figu

re o

f Mer

it

3 4 5 6 7100

2 3 4 5 6 71000

2

Energy (keV)

SM1 (PSPMT) SM2 (MAPMT)

Figure of MeritSM1 vs. SM2 Array

SM1 vs. SM2 Array

Despite the lower modulation factor, the FoM of the SM2 array exceeds that of the SM1 module.

The SM2 array provides :~25% greater sensitivity~30% smaller footprint~75% smaller volume

close-packing

LaBr3 Scintillator

1400

1200

1000

800

600

400

200

0

Cou

nts

200150100500Total Energy Loss (keV)

LaBr 3 (∆E/E = 9.5%) CsI (∆E/E = 25%)

GRAPE Energy Resolution(simulated)

Another important advance, in terms of energy resolution, will come from

the use of Lanthanum Bromide in place of the CsI.

Project Status

First science model successfully tested.

Now testing an improved design based on flat panel multi-anode PMT.

Engineering balloon flight of SM2 array in 2006.

Development of a full balloon payload for ULDB...

... a bunch of GRAPEs