Results from neutron irradiation at the OSU reactor.

Results from neutron irradiation at the OSU reactor.

October 2000 test

Conditions of the irradiation test.

- Six CSC front end anode boards have been irradiated, ## 58 68 70 79 86 87 (with CMP16F chips on them)

on Oct. 13, 2000. Prior to this test, on Aug. 28, the boards have been exposed to the 63 MeV proton beam

at the UC Davis with total ionizing dose of 5 krad delivered during 2.5 min.

- At the position the boards were placed in the OSU reactor they were given 2*10^12 n/cm^2 during 14 min 11 s.

The reactor power was 50 kW so the dose rate was 2.35*10^9 n/cm^2/s or 1.41*10^11 n/cm^2/min at the neutron

energy 100 keV < En < 10 MeV. There was also a significant gamma flux with effective dose rate of ~3.6 krad/min

which has provided the TID of 51.4 krad.

- The boards were powered in both exposures. The static parameters of the boards (voltage and current)

have been monitored during irradiation. No significant changes were recorded in the 63 MeV proton beam.

As to the neutron irradiation, the board regulator output voltage and voltages on pins 3,4 of the CMP16F chip

(preamplifier and discriminator parts correspondingly) have increased by 2-5% at the end of exposure.

Measurements of the board parameters and results.

- The board characteristics (thresholds, noise, gain etc) have been measured on the ASIC test stand at Fermilab

prior to the test in the proton beam, before and after the neutron irradiation. The set of tests after neutron

irradiation includes five measurements made with the interval of one - two weeks and with the first detailed measurement

taken 38 days after the neutron irradiation. The last three tests included one, one and four weeks of heating boards

in an oven at the temperature of 110 C degrees.

- The changes in the input threshold charge Qthr, Noise, Gain and the discriminator threshold Uthr vs time relative

to the day of proton irradiation are presented below. The results of the measurement taken before proton

irradiation are used as the reference (Qthr(0), Noise(0), Gain(0) and Uthr(0)). The arrows indicate the days when

the proton or the neutron irradiation took place, hyphens - how long the boards were heated in an oven prior to

the measurements.

Fig.1 (*.ps), (*.gif) - Qthr,

Fig.2 (*.ps), (*.gif) - Noise,

Fig.3 (*.ps), (*.gif) - Gain,

Fig.4 (*.ps), (*.gif) - Uthr.

Comments.

- All boards survived the irradiation by the 63 MeV proton beam.

- Only two boards (## 68,70) from six were working in the test taken 38 days after neutron irradiation.

The rest came to life after one week of heating in the oven at 110 C degrees. Five more weeks of heating brought

parameters of the boards closer to their reference values.

- The observed changes in the Qthr are due to corresponding changes in the gain and discriminator threshold Uthr.

There is no significant impact of irradiation on the noise.

Last modified: Mon Jan 29 15:00:00 CST 2001 teren@fnal.gov