C - Dipartimento di Fisica e Astronomia - Università degli Studi di ...

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C - Dipartimento di Fisica e Astronomia - Università degli Studi di ...

Development of a device for

Proton Radiography application

a) Dipartimento di Fisica, Università degli Studi di Catania

b) INFN, sezione di Catania

c) Dipartimento di Fisiopatologia Clinica, Università degli Studi di Firenze

d) INFN, sezione di Firenze

V. Sipala for the PRIMA collaboration

V.Sipala a,b , D.LoPresti a,b , N.Randazzo b ,

M.Bruzzi d,e , D.Menichelli e,d , C.Civinini d , M.Bucciolini c,d ,

C.Talamonti c,d , L.Marrazzo c,d , L.Capineri f , S.Valentini d,f

G.Cuttone g , G.A.P.Cirrone g , G.Candiano g , E.Mazzaglia g ,

e) Dipartimento di Energetica, Università degli Studi di Firenze

f) Dipartimento di Elettronica e Telecomunicazioni, Università degli Studi di Firenze

g) Laboratori Nazionali del Sud-INFN, Catania.


Outline

Motivations of a Proton Computed Tomography

Description of our Device

First results obtained

Conclusions

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

2


Proton Computed Tomography: why?

Advantages of proton beam therapy:

– Maximum dose

(Bragg peak effect)

– Finite range in tissue

(protection of tissues)

Main issues in the quality of treatment in proton therapy are:

─ Patient positioning

─ Dose planning

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

3


Proton Computed Tomography: why?

Patient positioning:

Currently performed using X-rays radiography in previous phase

PCT allows better accuracy and

Dose Calculation:

valeria.sipala@ct.infn.it

single phase positioning / treatments

Currently performed using X-rays computed tomography

Problem: protons and photons have

different interaction with matter

PCT uses protons directly for dose calculation

RESMDD08 October 17, 2008 - Florence

4


Parameters of Proton Computed Radiography

Proton beam rate

Spatial resolution

valeria.sipala@ct.infn.it

PARAMETER

Proton beam energy

Electronic density resolution

Detector radiation hardness

250-270 MeV

10 6 protons/sec

< 1 mm

< 1%

> 1000 Gy

VALUE

The critical parameter is the spatial resolution because of the multiple

Coulomb scattering of protons

RESMDD08 October 17, 2008 - Florence

5


Reconstruction Principle: Most Likely Path

A

L

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B

L’ L’’

A: Only entry position & direction known: straight line L

B: Entry position & direction + exit position known:

straight line L’

C: Entry position & direction + exit position & direction

known: curved path L’’, “banana-shaped”, narrow

confidence limits

RESMDD08 October 17, 2008 - Florence

C

6


Proton Computed Tomography concept

Reveal the trace of the single

proton using a silicon telescope

Measure the residual energy of the

proton using a calorimeter

Reconstruct the most likely path of

the single proton

valeria.sipala@ct.infn.it

Silicon

Telescope

Silicon

Telescope

RESMDD08 October 17, 2008 - Florence

Calorimeter

7


Proton Computed Radiography Device

valeria.sipala@ct.infn.it

4 x-y TRACKER MODULES

1 CALORIMETER

Entry and Exit

Residual Energy

position and direction

RESMDD08 October 17, 2008 - Florence

8


Single Tracker Module

Detector board

Microstrip detector

valeria.sipala@ct.infn.it

256

Vth

chip (x8)

DAC

256 DigOut

GEN

FPGA

Digital Board

control bus

address bus

data bus

Trigger

Trigger_en

Ethernet

Unit

RESMDD08 October 17, 2008 - Florence

9


Single Tracker Module

Detector board

Detector location

Digital board

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Detector board with a detector

and 8 chips containing the

electronic front-end.

1 x-y plane consists of 2 single tracker modules

RESMDD08 October 17, 2008 - Florence

10


Detector Description

53 mm x 53 mm

n-type substrate with

p-type implants

200 µm thickness

256 strips, each 57 µm

thick

200 µm pitch

Integrated resistance

for bias 1.5MOhm

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DC PAD

Substrate bias PAD

AC PAD

RESMDD08 October 17, 2008 - Florence

Guard ring

Bias ring

11


Electronic front-end front end description

Single

strip

Single channel

Charge

Sensitive

Amplifier

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Differentiator

(high pass)

Integrator

(low pass)

1.6 mm x 6 mm

32 channels

Power dissipation = 14,5 mW @ channel

Vcc = +3.3 V

Comparator Buffer

External

threshold

voltage

OUT

RESMDD08 October 17, 2008 - Florence

12


Calorimeter

4 YAG:Ce scintillating crystals

Each crystal 30 x 30 mm 2 x 100mm

4 Photodiode 18 mm x 18 mm

YAG:Ce properties

PHYSICAL PROPERTIES

Density [g/cm 3 ]

Hygroscopic

Chemical formula

LUMINESCENCE PROPERTIES

Wavelength of max. emission [nm]

Decay constant [ns]

Photon yield at 300k [10 3 Ph/MeV]

valeria.sipala@ct.infn.it

4.57

No

Y 3 Al 5 O 12

550

70

40-50

RESMDD08 October 17, 2008 - Florence

13


Calorimeter readout

Electronic front-end

Elettronic front-end

Electronic front-end

Electronic front-end

Tracker

modules

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AO 1-4

UF2-4000 14 bit

Digitizer/Oscilloscope

Trigger Generator Board

Σ

Trigger

+ -

Trigger_en

V threshold

Monostable

Event number

DAC

Counter

RESMDD08 October 17, 2008 - Florence

14


Laboratory measurements

Characterization of the detector board

Detector

Electronic front-end

Test of the complete detector board

Characterization of calorimeter

Single YAG:Ce crystal

Test of the 4-crystals calorimeter

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

15


Laboratory measurements

Characterization of the detector board

Detector

Electronic front-end

Test of the complete detector board

Characterization of calorimeter

Single YAG:Ce crystal

Test of the 4-crystals calorimeter

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

16


Detector characterization

3 detectors were tested. The following measurements were performed:

Leakage current vs Bias Voltage

Overall Capacitance vs Bias Voltage

Inter-strip capacitance vs. Bias Voltage

Comparison between curves measured at INFN (open circles) and by Hamamatsu (solid lines)

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

17


Laboratory measurements

Characterization of the detector board

Detector

Electronic front-end

Test of the complete detector board

Characterization of calorimeter

Single YAG:Ce crystal

Test of the 4-crystals calorimeter

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

18


Tests of the front end electronics

Only one sample (chip) tested

Characterization of single channel

Transient analysis

Input dynamic range analysis

Characterization of the full chip (32 channels)

Output pulse width dispersion

Noise occupancy

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RESMDD08 October 17, 2008 - Florence

19


Electronic front-end: front end: characterization of single channel

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Transient and input dynamic range analysis

Test signal

Output pulse

Input charge = Test signal (blue) on test capacitance

Digital unbuffered output pulse(green) @ C Load= 20pF

T rise = 130ns T fall= 80ns Width (@50%)= 720ns

Width (s)

760n

720n

680n

640n

600n

200MeV

20000 40000 60000 80000 100000 120000 140000

Input charge (e - )

RESMDD08 October 17, 2008 - Florence

60MeV

Tests made on one sample

All 32 channels characterized

20


Electronic front-end: front end: characterization of a single chip

650

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

valeria.sipala@ct.infn.it

Output pulse width dispersion

Output pulse width of 32-channels for fixed input signal and fixed threshold voltage

Width (ns)

740

730

720

710

700

690

680

670

660

Channel

Counts

6

5

4

3

2

1

Standard deviation = 17ns ( 2,5% )

0

620 640 660 680 700 720 740 760

Width (ns)

RESMDD08 October 17, 2008 - Florence

21


Electronic front-end: front end: characterization of a single chip

valeria.sipala@ct.infn.it

Noise occupancy

Noise occupancy is the number of noise output pulse per channel per time slice of 2ms

Noise occupancy (%)

100

80

60

40

20

0

1,56 1,58 1,60 1,62 1,64 1,66 1,68 1,70

Threshold Voltage (V)

100

80

60

40

20

RESMDD08 October 17, 2008 - Florence

0

22


Laboratory measurements

Characterization of the detector board

Detector

Electronic front-end

Test of the complete detector board

Characterization of calorimeter

Single YAG:Ce crystal

Test of the 4-crystals calorimeter

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

23


Test of the full detector board

Detector board: calibration of the detector + front-end front end chain

Efficiency of 32-channels vs threshold voltage for fixed input signal.

Plot shows typical data from a single chip.

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Efficiency

Efficienza

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

10mV

0

1.69 1.7 1.71 1.72

Vth(V)

1.73 1.74 1.75 1.76

V threshold (V)

RESMDD08 October 17, 2008 - Florence

Q IN =15000e -

24


Test of the complete detector board

Detector board: calibration of the detector + front-end front end chain

Output pulse width of 32-channels vs input charge for fixed threshold voltage

Plot shows typical data from a single chip.

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

25


Test of the complete detector board

Functionality testing with Sr90 source

Test of the complete detector board with radioactive source. We use a scintillator as trigger system

valeria.sipala@ct.infn.it

counts

60

50

40

30

20

10

0

0 0.5 1 1.5 2 2.5 3

released charge (electrons)

RESMDD08 October 17, 2008 - Florence

experiment

with noise

without noise

x 10 4

26


Laboratory measurements

Characterization of the detector board

Detector

Electronic front-end

Test of the complete detector board

Characterization of calorimeter

Single YAG:Ce crystal

Test of the 4-crystals calorimeter

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

27


Calorimeter

Test of a single crystal with a commercial electronic

readout (low acquisition rate) at Laboratori Nazionali

del Sud and Loma Linda Medical Center

normalized counts

1,0

0,8

0,6

0,4

0,2

0,0

0 200 400 600 800 1000 1200

channel

valeria.sipala@ct.infn.it

Center = 568,01

Width = 20,5

Resolution = 3,6%

Charge spectrum for 62 MeV

proton beam

FHWM Resolution %

30

25

20

15

10

5

20 25 30 35 40 45 50 55 60 65

Energy[MeV]

RESMDD08 October 17, 2008 - Florence

Measurements

1/E

Good

for high-energy

Input energy beam vs resolution

Counts

500

400

300

200

100

200MeV

Resolution about 1%

0

0 200 400 600

Channels

Charge spectrum for

200MeV

28


Laboratory measurements

Characterization of the detector board

Detector

Electronic front-end

Test of the complete detector board

Characterization of calorimeter

Single YAG:Ce crystal

Test of the 4-crystals calorimeter

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence

29


4-crystals crystals calorimeter: preliminary results

Test of the complete calorimeter with 62MeV proton beam

Counts

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1,0

0,8

0,6

0,4

0,2

0,0

0 3000 6000 9000 12000 15000 18000

Channel

Crystal 1

Crystal 2

Crystal 3

Crystal 4

RESMDD08 October 17, 2008 - Florence

30


valeria.sipala@ct.infn.it

Crystal homogeneity preliminary test

Irradiation of a single crystal on 9 different points.

Maximum variation is 1.2% with regard to the average value

~0.5cm

~1cm ~1cm ~0.5cm

3

2

1

0,966 1 0,988

0,995 0,976 0,965

0,981 0,999 0,992

0

0 1 2 3

RESMDD08 October 17, 2008 - Florence

0,9300

0,9922

1,000

31


Conclusions

A pCR device is being built by the PRIMA collaboration

Single tracker module

Single parts exist as prototypes

Detector board: complete (requirements quite satisfied)

Digital board: advanced development status

Calorimeter

YAG crystal: completely characterized

Front-end electronics: prototype exists (commercial parts)

Trigger generator: advanced development status

Future plans (by the end of the year)

Detector board: to be tested with proton beam (nov ‘08)

Digital board: coupling tests with the detector board (dec ’08)

4-crystals calorimeter: to be tested with 200MeV proton beam (nov ‘08)

Calorimeter front-end electronics: new design (higher rate)

Future plans (by the end of 2009)

Future plans (by the end of 2009)

Complete device built

valeria.sipala@ct.infn.it

RESMDD08 October 17, 2008 - Florence


Thank you for your attention

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