1. Readout Electronics for high-count-rate high-resolution
X-ray spectroscopy
Luca Bombelli, R&D Director
XGLab s.r.l., Via Francesco D’Ovidio 3, I Milano, Italy ,
14 April 2015, Pisa ERDIT

2. Products Services http://www.xglab.it Hybrid Electronics
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Services
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3. Expertise Detector Low Noise Front-End Processing and MCA Software
Primi due cruciali per performance (noise), secondi due per flessibilità
Processing and MCA
TWINMIC
ELETTRA
Software

4. SUMMARY
CUBE: new Front-End readout for detectors
DPP: High Rate X-ray spectroscopy (digital shaping)
VERDI-3: Versatile Electronics for Multichannel systems
High speed, 1-D Gamma Camera
for Prompt-gamma imaging

5. ASICs:
CUBE
A full CMOS preamplifier can replace the single front-end JFET
SDD
CUBE
Advantages:
High signal level at the output of the module.
No sensible loop outside the module.
Possibility to drive “long” connection.
Preamp Compactness
Superior performance respect to all the front-end JFET available at short shaping time.

6. Comparison with available JFET
0.2us
Measured energy resolution with identical SDDs
0.1us

7. Spectroscopy performances of CUBE connected to a SDD
1μs shaping time
(optimum)
ENC = 3.7e- rms
55Fe spectrum
123 eV FWHM
Commercial analog shaper:
7th-order Semi-Gaussian complex-pole

8. Spectroscopy performances of CUBE connected to a SDD
64mm2 SDD Squared
Ballistic deficit
Temperature
CUBE also suited for HPGE, SiLi and RTD
No worsening at cryogenic temperature

9. Digital Pulse Processor Platform
Optimized for CUBE
Input stage optimized for CUBE output
(dynamic range, gain, etc…)
Provide best possible energy resolution
Provide good performance at fast count-rate
(peaking down to 120ns)
Handle very high input count-rate
(ICR up to 3Mcps)
US patent: , , ,

10. SDD+ CUBE + DPP performances Energy Resolution Detector SDD
CUBE preamplifier
Temp= -60°C
Collim. Area = 50mm2
Signal rise = 300ns
Flattop = 330 ns

11. DPP
performances
Energy Resolution

12. DPP performances 98.5% dead-time 55Fe spectra
55Fe + X-ray tube spectra

13. DPP customization Supply: +/- 5V Power: 1.5W 10 cm
Compact single-board design, low power
Design to be reconfigurable and adaptive to several applications
Scalable to multi-cannel (in days chain mode)
High-performance 16-bit 105-MHz ADC. High performance FPGA
Possibility to add list mode operation
USB2.0 or Ethernet TCP/IP
Simple DLL libraries, or LabView
High throughput performance
Automatic Adaptive Filtering Mode

14. VERDI-3
Silicon Lithium
Detectors
Silicon detectors
(PIN, SDD, SSDD for gamma scintillator)
Germanium Detectors
(Segmented, Coaxial, Planar)
PMTs (or SiPM)
Multi-channel readout of different detector for several applications

15. VERDI Module 8 complete analog channels Single +5V power supply
USB2 interface, driver and DLL

16. Analog channel 2 polarity: electrons, holes
15 gains: mV (CSA range)
8 shaping times: μs
Selectable outputs: 1-pole pulse, 7 poles Shaper, PKS, KILL
BLH compensating detector leakage current: 0,1pA - 11nA
Variable SR, Gain, Bandwidth

17. XRF application with SDDs
VERDI config.
Pulsed-reset
Exernal preamp.
Internal shaper, PKS.
Energy range = keV
Output = Multiplexer
Fe55 Source
25mm2 single-anode SDD
Temp. = -30°C

18. Application with Ge VERDI config. continuous reset Input cap. = 50pF
JFET gm = 15mS
Range = 3keV - 10MeV
Output = 1-pole pulse
Resolution [eV]
Irradiation with a Co-57 source
Active volume = 34,2 cm2
Temperature = 70K
Digital filter Rise Time [μs]

19. Application with Si(Li)
VERDI config.
Pulsed-reset system
Input cap. = 2pF
JFET gm = 11mS
Output = 1-pole pulse
Resolution [eV]
Fe-55 source
Temperature = 70K
Detector area = 1,1cm2
Digital filter Rise Time [μs]

20. VERDI-3 Experimental setup Detector main characteristic:
Structured HPGe monolithic detector
Thickness 11mm
16 pixel with 6mm pitch
Pixel area 36mm2
Operation close to LN2 temperature
VERDI-3
HPGe crystal
Energy resolution with a Americium 241 source
Pixel with higher leakage current

21. Prompt Gamma imaging with a Slit Camera
High counting statistics
Simple design, reduced cost and limited footprint
Suitable to the measure of a single pencil beam
Most correlated energy range: 3 MeV ÷ 6 MeV

22. Specifications and design choices
Requested sensitivity: 15 cGy
Volume: 500 cm3 LYSO
(7.1 g/cm3 )
Event rate: 40 MHz
Pixelated design to reduce the rate in the single channel
Channel rate = 1 MHz
Fast crystal: τLYSO = 41 ns
Fast photo-detectors: SiPM
Fast electronics
Visible light output face

23. The prototype Back view Front view SiPM custom array:
7 SiPMs with 3 x 3 mm2 active area
LYSO slab:
31.5 x 100 x 4 mm3
Polished surfaces
Prompt Gammas
LYSO slabs in aluminum case (only 1 row of 20 slabs mounted)
Motherboard and backplane board

24. Calibration Clinical beam current Slow mode maximum event rate: 50 kHz
A/D conversion of pulse amplitude
Spectrum and energy calibration
Clinical beam current
Fast mode
maximum event rate: 1 MHz
3 MeV
6 MeV
Valid
event
Events discarded
Counting of valid events
Real-time profile reconstruction

25. Spectrum in slow operation mode (single channel)
No collimator in place
Beam energy: 100 MeV
Beam current at nozzle: 44 pA
Measurement time: 3 min
T = 25 °C

26. Experimental results: spectra in slow mode and thresholds setting
Energy calibration made with 137Cs source and the double escape peaks of Oxygen and Carbon
Exponential fitting to take into account SiPM saturation

27. Target shift detection
Beam d2
Reference position
(0 mm)
Beam energy: 100 MeV
Energy range: 3 ÷ 6 MeV
Time of acquisition: 10 s

28. Target shift detection
Beam d2
Reference position
(0 mm)
Beam energy: 100 MeV
Energy range: 3 ÷ 6 MeV
Time of acquisition: 10 s
1 mm

29. Target shift detection
Beam d2
Reference position
(0 mm)
Beam energy: 100 MeV
Energy range: 3 ÷ 6 MeV
Time of acquisition: 10 s
- 1 mm

30. Target shift detection

31. Thank you

32. Leakage and photons
CUBE output
55Fe signal
30 ns
SDD connected

33. CUBE operation over temperature
Pulsing SDD Ring1
200 ns
300 K
50 K
CUBE Rise-time < 40 ns
Irradiating with LED
300 K
3 us
50 K
300 ns
SDD drift time: 50K
300K

34. Setup for experimental measurements
Open collimator
Closed collimator

35. Profiles in fast mode Beam current at nozzle: 1.1 nA
Energy range: 3 ÷ 6 MeV
Time of acquisition: 10s
Open collimator
Closed collimator
All profiles are normalized to a uniformity flood acquired without collimator