L.Natalucci,WHIM Conference, Roma, 17-18 Jan 2006 CZT Wide Field Gamma-Camera for ESTREMO...

L.Natalucci,WHIM Conference, Roma, 17-18 Jan 2006

CZT Wide Field Gamma-Camera for ESTREMO

P.Ubertini, L.Natalucci, E.M. Quadrini and collaborators

IASF/INAF

b [deg]

l [deg]

INTEGRAL: coded mask FOV and source multiplicity

INTEGRAL/IBIS map of Cassiopeia region (20-50 keV)

mosaic 0.7-1.6 Ms, 0.4 – 12 mCrab, den Hartog et al. 2005

SPI

IBIS

XMM (30’)HMXB

SNR

AXP

ms-pulsar Diffuse emission (26Al, 60Fe)from Gal plane

Many different source types – outside GC and bulge !


• The high energy sky is highly variable and ToO’s are important

© M. Revnivtsev & E. Churazov, IKI Moscow/MPA Garching

3 deg

GC region, 17-60 keV, 12 frames (36 days)GC region, 17-60 keV, 12 frames (36 days)

The transient gamma-ray sky

Sources can appear in ~1000s

Or a few days

Or a few weeks

Rev 169 Rev 171

Sguera et al., 2005 A&A, in press



• CdZnTe pixellated detectors (energy band ~3-300 keV), which can be assembled in very compact, modular configuration

• Use of coded mask technique

Very large area, high resolution instrument can be achieved by natural extension of the INTEGRAL/IBIS concept

with much wider FOV to ensure detection of a large number of transient events, such as ~100/y

BeppoSAX/WFC heritage



The stopping power of CdTe/CZT keV is dramatically higher than Si,Ge (45% at 200 keV, for 3mm thick detector

100 keV Absorption Efficiency

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Thickness (mm)

Ab

so

rbti

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Si Ge CdTe

CdTe/CZT units are also:

• operating at room temperature

• performing well in space environment (low activation, fast recovery after solar flares)

• small pixel manufacturing, pixel arrays

• mass production is relatively low cost, and established technologyCdTe/CZT vs other



• CZT detection plane with improved characteristics, achievable within ~ 2 years.

• Effort to achieve extended performance, like <0.5 keV resolution for detection of X-ray features during prompt emission of GRBs and transients.

• Up to 10000 cm2 can be achieved for the sensitive area if high energy range is limited to ˜ 300 keV

WFGC detector

• Power consumption is, in average, 0.5-1 mWatt per channel; total required: ≤ 100 W for the whole unit FEE.

the ISGRI MDU

the ISGRI “polycell”



CZT: technology improvements

Need to improve CZT performances compared to present available commercial products. The goal is to achieve a factor 5-10 better energy resolution:

Improvement areas:

• Crystal growth and composition

• Surface treatment and contact depositions

• Front end electronics

• Digital processing electronics



R & D program in Italy for CZT developmentA program has started with a consortium of institutes/industries (P.I. M.Quadrini):

• IMEM-CNR for crystal development

• INAF Milan, Bologna, Rome and Palermo:

Detector development incl. AFEE, DFEE

Signal elaboration, Data Processing

Instrument concept and models

• AAA-I-Laben for AFEE studies

• VENEZIA Tecnologie for evaluation of mass production

Funding from ASI expected. Program already started



• wide FOV (~2 sr) and moderate angular resolution (down to ~ 1-2 arcmin) to detect and localize transient events

• monitoring capability, but also detailed characterization of prompt emission, like GRBs, fast transients, bright source outbursts

• extension of the mission range from X-rays to higher energies

Schematic of a possible configuration for one WFGC unit

2004 concept



We had in the first instance, considered two possible solutions, based on 2 mm and 3 mm thick CZT, respectively.

The effective area for 2mm and 3mm detector thickness.

Effective area

The thickness of the tungsten mask will depend on the chosen CZT thickness.



a coded mask design for the WFGC could be based on MURA pattern, with 2.4 mm pitch. The mask pitch is about 1.5 times the size of the basic detector pixel.

The mask is placed 1m from detector.

Imaging (an exercise)

• the coding power is 80%

• the Point Source Location Accuracy, PSLA < 1 arcmin for a > 10sigma detection. The PSLA depends on the signal-to-noise: for this configuration, is expected to be about 1.5 arcmin at the source detection limit.


Main difference from 2004 design:Limit the energy range to <300 keV (no 511)

Option 1Less area more FoV (4 detectors with smaller area)

Option 2• Completely new instrument FoV structure: annular mask and detector (similar to the

one of GRI-ESA Cosmic Vision Study):• Area 5,000-10,000 cm2• Single annular modular detector concept• Thin annular mask (0.5-1 mm W) • Wide field around the X-Ray telescope for shorter slew, fast repointing, transient event

always within the WFC FoV.• No high energy calorimeter (4-300 keV)

Plus 10-60 s on-target, lighter package, full time history for each det GRB

Minus not easy design, need R&D for detector performance electronics

Others On board SW and S/C autonomous operability, TL M resources management

Possible improvement




Option 1.

up to 4 different units located aside on S/C support

Option 2. (schematic, top view)

detector modules positioned on “annulus” on a support platform, mask ~ 75 cm from detector, sensitive area 7700 cm2

support struct

S/C

Mask envelope

1m36 CZT modules



Sky coverage option 2

~130O

Exposed area in FOV

Circular FOV shape



MASS AND POWER BUDGET OPTION 1

W mask 30 kg 15kgTube/Hopper, W 70 20 CZT detection plane 40 40Calorimeter/Veto BGO 30 30Electronics 20 10Structure 20 12Harness 10 satellite Contingency 20 13

Total: 240 140 x 2 units = 280 Kg

Power Budget 100 W 100 W x 2 units = 200WMASS BUDGET OF VERSION 2 UNDER ESTIMATION

2004 Light version



Energy range: 4-200 keV without response up to 511 Sensitive area 2300 cm2 (48 x 48 cm2) Energy resolution: 1 % (E>60KeV) Sensitivity: 1 mCrab/day, 20 mCrab in 2000s

(HEO E>40 keV, Solar max) PSLA: 20 arcsec Nominal ang. Resolution 10 arcmin Field of View: 90 x 90 deg @zero response (~2 ster)

(> 50% coding for offset angles <35 deg)

Summary of scientific performances option 1



New class of fast transients associated to HMXBs

IBIS detects them very well! (Negueruela et al. 2005)

IGR J17544-2619

Chandra (int’Zand et al 2005)

At least up to 7 objects detected of this kind



New class of fast transients associated to HMXBs

XTE J1739-302 = IGR J17391-3021

IBIS/ISGRI “zooming” on source outburst (Sunyaev et al. 2003)

RXTE/PCA (Smith et al 2005)


High localization accuracy is essential in many cases, and most important with improving sensitivity

Sources in molecular cloud NGC6334, as seen by Chandra

ISGRI error box

Hard X-ray source identified as a background AGN

(Bassani et al., astroph/0510338)


L.Natalucci,WHIM Conference, Roma, 17-18 Jan 2006 CZT Wide Field Gamma-Camera for ESTREMO...

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