2003/12/17 TIT irradiation we will study radiation effects in PIN and in RadFET at low temp.: - we will measure on-line the PIN diode gain drop at two different (known) dose rates - RadFET response at low temperature (10-15deg). A 500kRad (one day, 10:00-16:00) irradiation should be enough for our purposes. PIN --- # Pin diode response after preamp. (op.amp. with 8.2MOhm feedback resistor) ----------------------------------------------------------------------------- Pin diode No. A(mV) B(mV) Aminogray No. and (total dose) ----------------------------------------------------------------------------- 1 3.2 1.4 39 (182krad) 2 6.5 4.0 244 (0 krad) ----------------------------------------------------------------------------- RadFET ------ # RadFET No. Aminogray No. ----------------------------------------------------- RadFET No. 20030508 oldRadFET/3 243 (0 krad) ----------------------------------------------------- Setup ----- Source activity: 2003/3 20.7TBq Dose rate: 64kRad/h (10cm) 17.3kRad/h (20cm) 7.69 kRad/h (30cm) 4.34kRad/h (40cm) Irradiation start: 10:41 Irradiation end: 17:00 (6.31h) Dose at 10cm: 404 kRad Data file: 20031217-0000.txt Setup ----- Both boards with 4k range sensors each were placed at 10cm from the source. One of them was mounted on a frozen PET bottle, which provided almost constant temperature around 7deg, and another on a Pb block (at room temperature, 13deg). Initial readout voltage of all sensors was 9.5V, PIN at 10cm showed 1.75V and PIN at 20cm 0.42V. Signal from pin was amplified by an operational amplifier (TL082CP) with 8.2MOhm feedback resistor and lead to the Darwin logger via 7m long network cable. At 10:40 K 9.5 all PIN 1.75 1.75 0.42 0.42 At 14:00 K 8.74 8.59 8.39 9.23 8.79 8.93 6.18 9.35 Temp 7.3 12.8 PIN 1.68 1.69 0.418 0.419 At 16:00 K 8.7 8.5 8.35 9.2 8.75 8.55 4.97 9.33 Temp 7.3 12.8 PIN 1.65 1.65 0.415 0.42 at 16:50 K 8.68 8.49 8.32 9.16 8.71 8.45 4.45 9.28 Temp 7.2 12.9 PIN 1.63 1.64 0.41 0.42 First 4k readings are related to low temperature (7deg) and the other 4 to high temperature (13deg). We checked that the connections are correct by disconnecting one of the RadFET boards. Drop of all monitors at 7deg is very low (1V/300kRad), where in older irradiations at 20-25deg the drop was approximately 3V/300kRad. Monitors at 13 deg show simmilar behaviour, except from one of them, which dropped for 4.5V/300kRad. PIN signal decreased for about 0.1V/400kRad for diodes at 64kRad/h, and there was no visible decrease for 17.3kRad/h. We also tested for PIN signal linearity by placing the PIN at 30cm and 40cm from the source after the end of irradiation. at 17:00 PIN (10->30cm) PIN (20->40cm) The signals decreased as expected, at 40cm they were about 0.1V. After irradiation, RadFET were frozen (-15deg), transported to Tsukuba and connected to readout. Both boards were left to anneal at room temp. (which is now 15deg, same as Belle). Modules were connected to different readout channels of the RadFET reader as at TIT, but the voltage values of all sensors remained unchanged. As expected I will post first results tomorrow. --- About RadFET: They were irradiated at 7deg and 13deg (lower than any of the previous irradiations), but the response during irradiation does not differ from those at higher temperatures (green curve, plot 3 under RadFET plots). This time, we brought sensors back to the lab frozen to -17deg, so for the first time no annealing happened during transport (fig. 1, thanks Iwaida kun). We can see that 5 (out of 6) sensors behave strange (one recovered later, during annealing). We have now 1 live sensor from each board, the one at 7 and the one at 13 deg, and their responses are almost same, so we can see there is no large dependence on the environment temp. during irradiation. We had bad luck with many dead sensors this time, so we will need some more statistics, I suppose. About PIN: the signal decreases with the second power with the distance from the source (fig. 1 under PIN), which confirms the linearity of the PIN response with respect to the rate. Both PIN, those at 64kRad/h and those at 17.3kRad/h show some gain drop (see fig. 3 under PIN), but very small (in Belle, the gain drop was factors, not percent), and the slope of gain drop is different for the both rates (see fig. 2 under PIN). Tsuboyama san's suggestion was that in Belle, the major reason for gain drop are not photons (at least not those around 1MeV energy, but perhaps particle background). -- Samo Stanic University of Tsukuba, Japan