First results from silicon and diamond sensors

K. Afanasiev1, I. Emeliantchik1, E. Kouznetsova2, W. Lohmann2, W. Lange2

1 NC PHEP, Minsk2 DESY Zeuthen

2

CVD diamond :

Radiation resistant ( up to 10 MGy) Fast (charge collection time ~ 10 ps) Low dielectric constant => Low capacitance

but Low signal : < ½ signal from silicon

Charge collection distance dc: cccc

vis QQL

dQ

3

Si - Diamond comparison

 Silicon CVD-Diamond

Resistivity, ×cm 2.3×105 1013-1016

Carrier density, cm-3 15×1010 <103

Dielectric constant 11.9 5.7

Capacitance (1 cm2, 500 m), pF 35 17

Breakdown field, V/cm 3×105 107

     

Energy/(e--h pair), eV 3.6 13

Mobility, cm2/(V×s)e- 1350 1800 - 2200

h 480 1200 - 1600     

Average e--h number per 100 m (for MIP) 9200 3600

Energy deposition per 100 m (for MIP), keV 40 50

Charge collection distance dc, m   60 - 250; dc = f(l)

4

Test Set Up

5 mm SC. 2

SC. 1

Si/diamond

lead (for cosmics only)

Sr/cosmics

&

Gate

PA

discr

discr

delay

ADC

5

Test Set Up

6

PA+ADC calibration

y = 336.52x + 104.30

500

1000

1500

2000

2500

3000

0 2 4 6 8 10Q, fC

AD

C c

hann

elElectronics calibration PA : VV 50-3

(charge sensitive)

ADC : CAEN V265 12 bit

ENC = 700 e

(diamond sensorconnected )

gen

50

1 pF

Cw Cv = g·Cf

Cf

7

Sr source + triggering system

Sr

Y

E, MeV

Sr

Y

5 mm

90Sr

SC. 2

SC. 1

Si/diamond(300 m)

&

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Sr source + triggering system

Emip = 1.25 MeVdE/dx = 3.56 MeV/cmR = 0.3 cm Emip = 1.5 MeV

dE/dx = 5.57 MeV/cm R = 0.2 cm

=> ~mip - signal

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Signals from 90Sr – silicon :

Si(mip)

10

Signals from 90Sr – diamond : Selftriggering:

discr

delay

in

gate

ADC

PAdiamond

Sr

Diamond(noise)

Diamond(whole -spectra)

11

Noise level is not optimal for signal/noise separation Possible solutions :

Noise optimization of the existing preamplifieror

Switch to Amptek A250:

New trigger scintillator matching the size of the sensor

Problems and further steps :

Expected noise

≤ 350 e

12

Fraunhofer Institute (Freiburg) : (12 x 12 mm) 300 and 200 m Different surface treatments

Prokhorov Institute (Moscow)

(Dubna group)

Further steps :

New diamond samples :