Results from neutron irradiation at the OSU reactor.

Results from neutron irradiation at the OSU reactor.

July 2000 test

Conditions of the test.

- Seven CSC front end anode boards have been irradiated, ## 2, 3, 4, 18 (with CMP16F chips on them)

and ## 21, 23, 26 (with chips CMP16E irradiated earlier in the 63 MeV proton beam at the UC Davis

with total ionizing dose of 60 krad, 30 krad and 13 krad correspondingly).

- The boards were unpowered.

- At the position the boards were placed the measured neutron flux was 4.7*10**9 n/(cm**2 * sec)

at the neutron energy 100 keV < En < 10 MeV. There is also a significant gamma flux with effective

dose rate of ~7 krad/min.

- The boards were tested on the ASIC test stand at Fermilab a month later after irradiation.

Data and specific operating conditions.

- Table 1. Doses for boards. Note that the neutron fluence is 0.6*10**12 n/cm**2 and

gamma TID = 1.78 krad for 10 years of LHC operation.

Board #	Neutron dose (1012 n/cm2)	Time	Gamma dose (krad)	Comment
2	1.2	4 min 15 sec	30.8	CMP16F
3	1.8	6 min 23 sec	46.3	------
4*	3.0	10 min 38 sec	77.1	------
18*	6.0	24 min 17 sec	154.3	------

21*	1.2	4 min 15 sec	30.8	CMP16E, after proton TID of 60 krad
23*	1.8	6 min 23 sec	46.3	CMP16E, after proton TID of 30 krad
26*	3.0	10 min 38 sec	77.1	CMP16E, after proton TID of 13 krad

The boards marked with * did not work after irradiation.

Results.

- Only 2 boards (## 2,3 - CMP16F) survived after irraditon with dose equivalent to doses of 20 and 30 LHC years.

The others, for example, boards ## 4 and 18 have much higher threshold (300-400 fC) and much bigger noise.

The parameters of board #2 before and after neutron irradiation are given in Table 2 (board #3 has similar behaviour).

The Average and RMS characterize the parameter distribution over 14 channels of the board ( 2 channels with

max. and min. excluded). Max-Min is the difference between maximum and minimum values of the parameter

within 16 channels of the board.

- Table 2. Board #2 parameters before and after irradiation.

Average

When	Qthr, fC	Noise, fC	Gain, mv/fC	Offset, mV
Before	17.6 +- 0.3	1.5 +- 0.02	8.9 +- 0.04	51.6 +- 2.6
After	18.3 +- 0.3	1.2 +- 0.01	12.6 +- 0.05	-22.7 +- 4.1

RMS

When	Qthr, fC	Noise, fC	Gain, mv/fC	Offset, mV
Before	1.23	0.06	0.16	9.55
After	1.31	0.05	0.18	15.27

Max - Min

When	Qthr, fC	Noise, fC	Gain, mv/fC	Offset, mV
Before	4.89	0.50	0.75	42.31
After	4.69	0.23	0.99	54.17

- Looks like the gain and the discriminator offset are much more affected by the neutron irradiation than

by the proton beam. The board depicts the different picture of the threshold's and offset's behaviour after neutron

exposure. The gain increased by 40% compare to a rise of a few percents at the dose of 5 krad in the proton beam.

Also the change in the discriminator offset is quite large and has a sign opposite to one in the proton beam.

The good news is that as a combined result of two opposite contributions the threshold increased by 4% only.

- The time resolution (RMS) was not deteriorated by the neutron irradiation. It remains to be less than 1 nsec.

at Qin=100 fC and Qthr=18 fC.

Last modified: Mon Nov 27 16:00:00 CST 2000 teren@fnal.gov