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Sensori spettroscopici sensibili alla posizione in 3D per raggi X e gamma

Primo Workshop Nazionale su:La Componentistica Nazionale per lo Spazio:

Stato dell’arte, Sviluppi e ProspettiveAgenzia Spaziale Italiana (ASI)Roma, 18‐19‐20 gennaio 2016

Ezio Caroli (INAF/IASF‐Bologna)

a nome di una collaborazione:INAF/IASF‐Bo/Pa e CNR/IMEM (Parma), Due2Lab S.r.l. (Parma)

DTU Space (Lingby, Danimarca) LIP (Coimbra, Portogallo)

ASI Workshop Components4Space (Roma, 18‐20 Jan 2016) ‐ E. Caroli "Sensori spettroscopici sensibili alla posizione in 3D per raggi X e gamma" 2

ABSTRACT:La nostra collaborazione è impegnata da diversi anni nello sviluppo di sensori spettroscopici per raggi X duri e gamma molli basati su CZT e sulla tecnologia delle drift strip in grado di determinare la posizione di interazione dei fotoni in 3 dimensioni. Questi sensori, usati come unità elementari, possono offrire una efficiente risposta agli stringenti requisiti per la realizzazione di piani focali ad elevata efficienza di assorbimento e prestazioni (spettroscopia e imaging) come quelli richiesti dalle nuove tecnologie di focalizzazione in raggi X duri e gamma molli (Lenti di Laue a larga banda e Concentratori Multilayer di ultima generazione) che rappresentano uno dei scenari più interessanti per le nuove missioni in questo intervallo di energia (10‐1000 keV). Questi sensori possono offrire interessanti applicazioni anche in altri settori come l'analisi non distruttiva di materiali pesanti in ambiente industriale, nei controlli di sicurezza sui trasporti commerciali e nel monitoraggio ambientale.

Table of contents

Perspective for Hard X‐ and soft‐gamma ray astronomy : Broad band Laue lens

3D Spectro‐Imager: Requirements and Advantages

3D spectro‐Imager developments

3D sensor unit preparation

3D spectro‐imager units characterisations

Conclusions


Perspective for Hard X‐ and soft ‐ ray astronomy : Broad band Laue lens


At least a two–order of magnitude increase in sensitivity and angular resolution, withrespect to current instrumentations, in the energy band up to several hundreds of keV(600‐700 keV) is required to be able to solve several still open hot scientific issues.

These requirements can be fulfilled only with space telescopes implementing new highenergy focusing systems. The current development of broad band Laue Lens offer thebest technical and more challenging solution for the realization high sensitivitytelescope above the current limit (80 keV)

One of the main advantage of Laue lenses based telescope, with respect to multilayertypes, is that we can extend the band up to 600/700 keV with a focal length of about20 m, which is still feasible with a single satellite.



ASI funded in 2009 a project for the development of a new type of broad band Laue lens for hard X and soft ray astronomy.

Italian collaboration of research institutes (University of Ferrara, CNR/IMEM‐Parma, INAF/IASF‐BO/PA) and industries (DTM Technologies – Modena, Thales‐Alenia Space –Milano and Torino) – leadership in europe

Broad band Laue (90‐300) Lens using a dedicated X‐ray beam line at the LARIX facility located at the Physics and Earth Science Department of the Univ. of Ferrara.



One of the most challenging results are the innovative crystal bending techniques developed to improve the focussing performance of the Laue lens.

With bent crystals it is possible to achieve two key goals: a much better focusing and a higher reflectivity (> 50%, i.e. the intrinsic limit of mosaic crystals).

1.2 mm

14.4 mm

• PSF obtained by using a ring

GaAs (220) @ 157 keV



High detection efficiency, achievable with increased thickness (>80% at 500 keV); Fine spectroscopy (1% FWHM at 511 keV) achievable with small volume charge

collection; Fine spatial resolution (<0.5 mm) achievable with high segmentation. Scattering polarimetry in parallel to spectroscopy, imaging and timing

Thick (10‐15 mm) bulk CZT with pixelated electrodes: the strong pixel effect allow the depth reconstruction of interaction.Drawbacks: hight low energy threshold; charge sharing

Stack of several very thin detection layers. Drawbacks: (a) complexity of electronics and mechanical

assembling; (b) the presence of a lot of passive material between each layer (unwanted scattering)



The advantages 3D CZT spectro‐imager, with respect to present CZT spectrometer and imagers, can be highlighted as follows:

Improve the efficiency and consequently the sensitivity using Compton events in addition to the photoelectric ones;

Possible rejection of environmental and instrumental background, e.g. using Compton cinematic;

Uniform response achievable by means of signal compensation techniques; Very low degradation of the point spread function of the flux focused by a Laue lens or

similar optics with energy because of the possibility to identify the photon interaction points in scattered events.

High efficiency scattering polarimetry in high energy astrophysics above 100 keV; Fine spectroscopy also for multiple events because each hit signal come from a small

sensitive (voxel)



Compton imaging and background rejection

Scattering Polarimtery:Scattering map at 200 keVModulation curve at 200 keV

3D Spectro‐Imager development.


PTF irradiation configuration:Decoupling between photon absorptionthickness and charge collection distance

The anode side electrodes are modified to make the detector more sensitive to electron collection and less sensitive to hole collection.

The Anode (top) side implement a drift strip configuration; The cathode

segmented orthogonally (bottom)

3D Sensor Unit

3D spectro‐Imager development


SGRIP (PRIN INAF 2007): First implementation of anode drift strips and ortogonallysegmented cathode on CZT sensor in PTF configuration

Anode side Cathode side

The Linear Module

3D spectro‐Imager development


The linear module are packaged together in a light‐tight Al box. This box provide both the linear module support, minimizing as possible the gap between each module, and the mechanical I/F with the AFEE board.

8 identical modules packed together (64 anodes and 32 cathodes)

Beryllium window100 micron thick

Temperature and humidity control by fluxing dry air or Nitrogen

Mechanical I/F withthe AFEE Board

3D Sensor Unit preparation


ESA independent R&D development project:“3D CZT High Resolution Detectors 4000104191/11/NL/CBi”

Redlen CZT Material

20 mm x 20 mm x 5 mm

Cathode: 10 strip 2 mm pitch

Anode: drift strip configuration,



Detector preparation

1. Mechanical polishing of 20x20x5 mm3 spectroscopic grade crystals from REDLEN

2. Metallization 1 (anode collecting strips and cathode strips): Gold chloride electrolessdeposition

3. Surface passivation on anode surface: Al2O3 deposition by Pulsed Electron Deposition (PDE)

4. Metallization 2: Thermal evaporation of copper/gold contacts (drift strips)



Leakage currents between adjacent stripes are less than 2 nA @ 100V!!!

Bonding 200 micron stripswith silver paste


3D Spectro‐imager unit characterisation3D sensing capabilities

- resolution along Y direction

- resolution along X direction

- resolution along Z direction

Spectral performancesScans performed in PTF configuration at 150, 300,

400, 580keV:

x-y scans - x: 26 steps, y:28 steps (5.2 mm x 5.6 mm)

z-y scans - z: 40 steps, y:4 steps (24 mm x 3.2 mm)

Only 4 drift cells were tested

z

y

x

beamxy scan

beamyz scan

ESRF ID 15 A

BEAM SIZE 0.05 mm X 0.05mm


3D Spectro‐imager unit characterisation

Y position can derived from:

Resolution is given by the FWHM of the gaussianobtained with 15K events:

XY Scan: Y position (Depth sensing)

Depth Sensing Relation


3D Spectro‐imager unit characterisationXY Scan: X position

X = Xn + (DR‐DL)/(DR+DL)Beam Position


3D Spectro‐imager unit characterisationYZ Scan: Z position

YZScan

10 cathodes

Each photon

One point scan


3D Spectro‐imager unit characterisationEnergy resolution

2 2 2detTot sync EletE E E E


3D Spectro‐imager unit characterisationThe test demonstrated that the proposed sensorunit is a X and gamma ray detector with high energyresolution and 3D imaging capability.

Best performances at 400 keV:x = 0.15 mmy = 0.26 mmz = 0.65 mmE (FWHM): 1.4%

PERFORMANCES COMPLIANT WITH THE NEW HIGH ENERGY FOCUSING SYSTEM (LAUE and Multilayer)


Some recent projects submitted to Italian Institution Calls3D Focal plane prototype for wide band (60-600 keV) Laue lens – TECNO INAF

2014Development of an innovative 3D spectro-imager prototype for broad band (60-

600 keV) Laue lens telescope – ASI Bando per nuove idee di strumentazione scientifica per missioni future di osservazione ed esplorazione dell’universo DC-EOS-2014-309 (2014)

Projects just submitted or in definition High performance 3D CZT spectro-imager for X and gamma-ray applications –

PRIN MIUR 201

COMPET-01 (COMPETITIVENESS OF EUROPEAN SPACE SECTOR: TECHNOLOGY AND SCIENCE - H2020) – large European colllaboration(CEA/Sacaly, INAF/IASF, IMEM/CNR, DTU Space, ICE/UAB, LIP-Coimbra....)


PRIN MIUR 2015 (Univ. of Pavia, IMEM/CNR, INAF/IASF-Bo, Univ. of Palermo

New configuration of the 3D CZT sensor unit and associatedlinear module: AFEE implemented in each linear module.

The packaging (left) is 2 side «buttable»: easy assembling of a 2x2 mosaic (4x4 cm2)

Tests of 3D CZT module as Laue lens focal plane and as a scattering polarimeter (Laue X ray beam at the LARIX facilityand ESRF)

The 3D CZT stack module is proposed also for medical and fundemental physics: (a) BNCT (Boron Neutron Capture therapy)-SPECT (478 keV); (b) Measurement of the Zemach radius of proton (100-700 keV)

Short term perspective and conclusion


From R&D phase we shall go to the engineering phase. The target is to obtain a “space qualified” 3D CZT spetro-imager module that can be assembled in suitable way to obtain the required sensitive area. Much greater scale of investments are needed in future.

Project in definitionCOMPET-01 (COMPETITIVENESS OF EUROPEAN SPACE SECTOR: TECHNOLOGY AND SCIENCE - H2020) – large European colllaboration (CEA/Sacaly, INAF/IASF, IMEM/CNR, DTU Space, ICE/UAB, LIP-Coimbra....)

Short term perspective and conclusion


Grazie a tutti per l’attenzione!

Grazie all’ASI per l’opportunità di presentare questa attività di R&D, che noi riteniamo strategica, nell’ambito del primo Workshop dedicato alla Componentistica per lo Spazio!

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