Cold tests of irradiated FE-I4 at CERN

M. Menouni , A.Rozanov

(CPPM - d'Aix-Marseille Université)

Cold tests of irradiated FE-I4 2Aout 12, 2013

Outlook The test set-up and the test conditions Default configuration parameters Digital tests Noise Occupancy tests and Low temperature effects Effects of PrmpVbp and Amp2VbpFol on the Noise at low

temperature Effect of the tuning at low temperature Conclusion

Cold tests of irradiated FE-I4 3

Test Set up Single board FE-I4-B number 165

irradiated in 2012 at CERN PS with 24 GeV protons close to the region of end of columns at 400 MRad

USBpix board with gray flat cable to single chip board

Typical consumption at ambient temperature is : Vdda=2.5v Idda=430 mA Vddd=2.5v Iddd=181 mA

Temperature regulated inside the freezer FARK 3130A with dry air flow

Noise measured with NoiseOcc scan usually with 10**5 pixel headers.

Aout 12, 2013

Cold tests of irradiated FE-I4 4

Default configuration Chip configuration: The threshold is set to 3000e

at ambient temperature FEI4b.irradiated.chip.165.tune

d.3000e.TOT8.cfg.root from 17.04.2013

in fact the configuration file corresponds to a non-tuned chip

Threshold Scan gives : Mean=3030 Sigma=381 Noise= 105 +/- 15

Aout 12, 2013

Cold tests of irradiated FE-I4 5

Digital Tests• Digital_Test good for nominal

configuration parameters: Amp2Vbpf=100

• Very High noise at small value of Amp2Vbpf=5

• block the discriminator, so the 400 MRad beam spot is clearly seen.

Aout 12, 2013

Amp2Vbpf = 100 Amp2Vbpf = 5

Cold tests of irradiated FE-I4 6

Noise Occupancy tests• Noise Occupancy scan is

compatible with the Digital Test• For nominal value of Amp2Vbpf

(100) ~No noise at room temperature

• For low value of Amp2Vbpf (=5) • Strong Noise at room

temperature• correlated with Beam Spot• In this test 64501 hits/10**5

headers

Aout 12, 2013

Amp2Vbpf = 100 Amp2Vbpf = 10

Cold tests of irradiated FE-I4 7

Noise Occupancy tests at T=-22 C• At -22 C and for nominal

configuration Amp2Vbpf (=100) • the Noise Occupancy is higher

than the noise at room temperature

• The level of noise is still acceptable

• For low value of Amp2Vbpf (5) • High level of noise• correlated with Beam Spot• In this test 43764 hits/10**5

headers

Aout 12, 2013

Amp2Vbpf = 100 Amp2Vbpf = 5

Cold tests of irradiated FE-I4 8

Effect of low temperature Nominal Configuration:

PrmpVbp = 43 Amp2VbpFol = 26

Noise increases for low temperature

For nominal value of Amp2Vbpf=100 : Noise starts to increase

at T~-10 C At T=-23 C Typical

3000 hits/10**5 headers

The noise still present even for Amp2Vbpf = 255

Aout 12, 2013

Cold tests of irradiated FE-I4 9

Effect of PrmpVbp at low temperature

Nominal Configuration: PrmpVbp = 43 Amp2VbpFol = 26

PrmpVbp is the bias of the peamp stage

Increasing PrmpVbp from 43 to 96 does not help to reduce the noise

Increase the consumption of the Preamp stage

Vdda current consumption increases from 430 mA (nominal) to 640 mA

30% increase of power

Aout 12, 2013

Cold tests of irradiated FE-I4 10

Effect of Amp2VbpFol at low temperature

Amp2VbpFol is the bias of the Amp2 follower stage

Decreasing Amp2VbpFol from 26 to 1 reduces the noise

but the noise level remains high even for the highest value of Amp2Vbpf (255)

Aout 12, 2013

Cold tests of irradiated FE-I4 11Aout 12, 2013

Low temperature effect for Tuned chip

Room Temperature (+25 °C)

Low Temperature(-26°C)

Low Temperature(-26°C)

Target Threshold (e) 3000* 3000* 2500*

VthAlt-Fine 140 200 140

Mean threshold value 2983(*) 3006(*) 2501(*)

Threshold dispersion 53 53.4 53

RMS Noise 108 +/- 16 198 +/- 16

Noise Occupancy

Amp2Vbpf = 255 0 0 0

Amp2Vbpf = 100 0 10 114

Amp2Vbpf =40 229 12175 27773

(*) The threshold tuned with the nominal configuration where the Amp2Vbpf=100

The threshold depends on the Amp2Vbpf We have to tune the chip for each Amp2Vbpf value changing !

Cold tests of irradiated FE-I4 12

Low temperature effect for Tuned chip

Test is done with Nominal Configuration: PrmpVbp = 43 and

Amp2VbpFol = 26 At low temperature of -26 °C,

the threshold is tuned to 3000 e- for the whole array of the irradiated chip

The noise occupancy is reduced drastically compared to the one for the un-tuned case at low temperature

Aout 12, 2013

Cold tests of irradiated FE-I4 13Aout 12, 2013

Conclusion Noise occupancy tests are carried out on the FE-I4 chip 265 irradiated with 24

GeV proton to 400 Mrad Below T=-10 °C, noise increase at nominal setting in few pixels Partly correlated with irradiated region of the chip At low values of Amp2Vbpf linear increase of the noise when lowering the

temperature At low temperature, Increasing the PrmpVbp to 96 or decreasing Amp2VbpFol

from 26 to 1 help to reduce the noise However, the noise level remains high even for the highest value of Amp2Vbpf

(255) Despite this level of noise, the threshold was tuned at 3000 e- for the whole

pixel array at low temperature The noise occupancy is reduced drastically compared to the one for the un-

tuned case at low temperature More details in E-log: https://atlpix01.cern.ch/elog/FE-I4_SEU_measurements/302