large area silicon drift detectors for x-ray spectroscopy and...

Large area silicon drift detectors for X-ray spectroscopy and imaging

Valter Bonvicini – INFN Trieste

XCIX Congresso Nazionale SIF Trieste, 23 – 27 settembre 2013

Contents

• Silicon Drift Detectors: basics

• The starting point: the XDXL experiment

• Developments: optimized large area SDDs and low noise FEE for X-ray spectroscopy and imaging (the ReDSoX experiment)

• Applications: – Astronomy: the LOFT Mission

– SDDs for experiments at Advanced Light Sources

• Conclusions

9/24/2013 V. Bonvicini - XCIX Congresso SIF - Trieste 2

Linear Silicon Drift Detector

• Gatti and Rehak, 1984; • “Sidewards depletion”; • Double-sided device with electrodes biased in such a way to create a potential minimum for electrons in the middle plane of the wafer; • The structures on the two faces are symmetric everywhere but in the collection region, where the electrons have to be “pushed” towards the anodes to be collected; • Small dimensions of the collecting anode(s): small capacitance low noise! • 2-D position information without ambiguities • For high performance the starting material should have a highly uniform doping concentration NTD material.


Linear Silicon Drift Detector

• “Butterfly SDD”: by means of a series of cathodes (biased with a linearly scaled potential) a uniform drift field is established from the center of the wafer towards two arrays of anodes, placed at opposite sides of the device.


The starting point: the XDXL project

• X-ray Drift eXtra Large • Active 2010 – 2012 • Outstanding characteristics of the large area ( 8 x 7

cm2) linear SDD realized within INFN for the ALICE Inner Tracking System @ LHC: Aims at verifying its characteristics as X-ray spectroscopic

detector

• Several applications could be envisaged: Medical field: Compton camera Nuclear physics precision spectroscopy X-ray astronomy/astrophysics X-ray imaging for Advanced Light Sources (SR and FEL)


ALICE-D4 SDD


Detector set-up for first tests at Rome-IASF X-ray facility


Front-end

electronics

Detector set-up for first tests at Rome-IASF X-ray facility


Room temperature spectroscopic performance of the ALICE SDD (2010-2011)


• Very good noise performance: ENC = 25 e- rms @ +20 °C

using a sub-optimal front-end electronics, only 2 worse

than the best commercial SDDs operated below -20°C

• Good energy resolution for such area: < 570 eV FWHM @

20 °C with a full instrumented ASIC read-out (realistic

simulation)

2-D imaging with photons?

• Not only spectroscopy: detector segmentation allows 2D imaging (in ALICE spatial resolution for MIPs better than 30 μm for both axis)

• X-ray anodic resolution better than few tens of μm down to 2 keV

• X-ray drift length reconstruction by exploiting the signal charge diffusion (no prompt trigger available) coarse drift resolution better than 6 mm (E ≥ 3.5 keV)


2-D imaging with photons?


XDXL: SDD development with FBK: first prototype run (2010) on 4”

• First run to evaluate the fabrication process and gather the informations required to optimize the detector in the following iterations


First FBK run: power consumption reduction


XDXL: second prototype run with FBK (2011)

• Largest SDD area in 4” wafer; leakage minimization; large anode pitch to optimize energy resolution in a detector half, small anode pitch for imaging in the second half.


The second FBK prototypes include design modifications (drift cathodes have been enlarged keeping the same pitch). In this way the potential minimum under the oxide is pushed closer to the surface and the dead volume in the substrate is reduce by a factor of about 4

Improvement of QE at low energies


Third FBK prototype production (2012)


LOFT: scientific objectives


The LOFT satellite


Spectroscopic SDD prototype


Total sensitive area of the matrix 135 mm2

Wafer thickness 450 µ

Spectroscopic SDD prototype

• Uniform, metal-free entrance window

• Entrance window optimization is required to extend the sensitivity to X-ray energies as low as 200-300 eV (Advanced Light Sources applications)


Mounted SDD prototype


Spectroscopic SDD results


- 16°C

Preamplifier: AMPTEK A250F-NF with external input transistor: SF-51 JFET (CGS = 0.4 pF)

ReDSoX: Research Detectors for Soft X-rays

• Linea di ricerca: development of large area ADDs and low noise front-end electronics for X-ray spectroscopy and imaging.

• Participants: TS, BO (IASF-BO), ROMA2 (IAPS-ROMA), MI (Politecnico), PV (UniPV)

• Collaborations: FBK (Trento), Sincrotrone Trieste

• Project timeline: 2013-2014


ReDSoX: fourth run with FBK

9/24/2013 V. Bonvicini - XCIX Congresso SIF - Trieste

• NIEL di protoni soft producono un incremento della corrente di leakage inferiore al previsto (~30%) possibilmente dovuto ad una maggiore ricombinazione iniziale tra vacanze ed atomi interstiziali nella regione del picco di Bragg

• l’annealing procede come previsto da vari studi sull’irraggiamento di dispositivi di silicio

Irradiation tests for LOFT: soft protons (800 keV)

NIE

L cu

rren

t [p

A]

NIE

L cu

rren

t [p

A]

9/24/2013 V. Bonvicini - XCIX Congresso SIF - Trieste 29 29

Irradiation tests for LOFT: iron debris


Front-end ASIC: preliminary results Poli MI – INFN Pavia

ReDSoX: SDDs for experiment @ ALS

• First approach: a pixel SDD optmized for fluorescent spectroscopy using synchrotron radiation light (experiment TwinMic@Elettra)

• 20 square cells (9.5 mm2) + 8 triangle cells (4.75 mm2)


Trapezio


ReDSoX SDD for TwinMic: first results

SDD «Trapezio» connected to a VEGA ASIC (Poli MI, G. Bertuccio) developed for linear SDDs

RIVELATORE TRAPEZOIDALE

10 mm2 quad-SDD read out by the VEGA-1 low-power front-end ASIC for X-ray

spectroscopy/imaging in space applications

M. Ahangarianabhari et al., VEGA-1: A Low-Power CMOS ASIC for X-Ray Silicon Drift Detectors Low-Noise Pulse Processing, IWORID 2013, 23-27 June 2013, Paris, France, soon submitted to Journal of Instrumentations

420 µW/ch

180 pA @ +22 °C - 30°C

Semiconductors and Integrated Circuits Laboratory Via Anzani 42, Como, Italy

ReDSoX Meeting - Trieste 4 July 2013 p.36/4

0 1 2 3 4 5 6 7 80

1000

2000

3000

4000

5000

6000

Pulser

PMC-ULNpre3

TS-FBK SDD E10

T=-40°C

tpeak

=12.8s

55Fe

35 eV

FWHM

(4 e- r.m.s.)

6.49 keV

5.9 keV

C

ou

nts

Energy (keV)

125 eV

FWHM

PMC-ULNpre3 ASIC coupled to TS-FBK E10 SDD

- 40°C


Conclusions • The INFN technology for large area SDD is currently the most

advanced in the world. Strong interest in further developing it (especially concerning QE): Detectors for Advanced Light Sources ESA LOFT mission (X-ray astrophysics)

• Very good results obtained up to now (XDXL and ReDSoX experiments). Next steps: LOFT: in 2013 we designed and realized (with FBK) the 76 cm2 SDD

for the LAD, tests will start next week; the 46 cm2 SDD for the WFM will be realized in 2014. ESA will take a final decision on which project will go to the final phase (“decision phase”) in January 2014.

Detectors for Advanced Light Sources: “Trapezio” SDD interfaced to a ultra-low noise front-end ASIC PMC-

ULNpre3. Design an ad-hoc front-end ASIC for the TwinMic application (Poli Mi) Design an alternative front-end based on a CSA followed by a delta-

sigma modulator Introduce an optimized “thin entrance window” for the detectors in the

next run.

large area silicon drift detectors for x-ray spectroscopy and...

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