Status of the PiN diodes irradiation tests B. Abi( OSU), R. Boyd (OU), P. Skubic (OU), F. Rizatdinova (OSU), K.K. Gan (Ohio State U.)

Oklahoma responsibility Our goal is to identify radiation hard high speed PiN diodes and measure their lifetime. High speed PiN arrays available on the market are GaAs or InGaAs. Radiation tests performed by KK in August 2007 have revealed that most of these devices are not radiation hard. 2

PiN diodes in our tests Contacted Hamamatsu to get the Si PiN diodes. Got two types of single PiN diodes to test them this spring/summer –S –S In case of success have an agreement that Hamamatsu will produce arrays for us. In addition, purchased Hamamatsu GaAs PiN diode, G8255 –Actually there are 3 varieties of this PiN: G , G , G –Difference is in the size of chip and in the speed 3

Characteristics of selected PiNs S : –2 GHz; –Active area d = 0.1mm; –Spectral response range 320 – 1000 nm; Peak sensitivity wavelength 700 nm; –Reverse voltage 2 V; S5973 –1.5 GHz; –Active area d = 0.4 mm; –Reverse voltage 3.3 V G8522 (3 types) –for all of them reverse voltage is 2 V; –Spectral response range from 570 to 870 nm; Peak at 850 nm –G : 3 GHz; Active area d=40  m – G : 1.9 GHz; Active area d=80  m –G : 1.5 GHz; Active area d=120  m 4 This information is from data sheets, available online from Hamamatsu web page

Performed irradiation tests TID test at BNL –Total dose 10 Mrad; –Passive test; 2 tests with protons at IUCF –200 MeV protons; –Total dose 80 Mrad (two times of 40 Mrads); –Online readout current of PiN diodes Temperature was within the range C° 5

TID test TID test with gamma rays at BNL together with SMU performed on April –Tested three G8255 and one S diodes, all have been biased. –Responsivity was measured offline at 0 Mrad, 5.6 Mrad and 9.6 Mrad Homogenous IR LED source biased by constant current was used to illuminate the PiN diodes for the responsivity measurements. –For each dose made 5 measurements, varying the optical power of the IR source from 2 to 10  W. –Measurements were averaged to get better understanding of the true responsivity. 6

TID results 7 Conclusion: No degradation has been observed for any type of tested PiNs in TID test with 10 Mrad

Test with protons at IUCF Performed in May and June at IUCF: 200 MeV protons –Have neutron source too, can be used; –Charge $550/hour, min number of hours to purchase is 12. Used 10 PiNs, two of each available PiN diodes Did not package them –Did not have a possibility to do that at Oklahoma; Used IR LED sources to illuminate PiNs One of each type of diodes was coated with radiation hard resin, another was a bare chip Started irradiation with very low flux, increased it gradually Got 40 Mrad in May and 40 Mrad in June. Still have not done full analysis of results obtained in June – will have in ~ two weeks. 8

Setup 9 Board with PiN diodes IR Source together with the board Setup installed in front of the proton beam exit

Results of irradiaton test with protons Example: Responsivity vs dose for all types of the detectors in the region between 16 and 29 Mrad. Responsivity of all diodes coated with resin is lower compared to bare ones The thickness of the resin varies for each type of PiN (added by hand at Oklahoma State U.) 10

Resin vs no resin (cont’d) 11 After 40 Mrad: dark are PiNs with resinBefore irradiation

Relative responsivity Compare all PiNs without resin in the same dose region, from 16 to 29 Mrad S and G have very similar behavior 12

Annealing effect We had a 5 hours break in data taking – cyclotron was off for maintenance. The total dose before the break was 3.7 Mrad. 13

Responsivity vs dose Si S and GaAs G look very promising. After 40 Mrad, the responsivity went down by ~ 25%. 14

Preliminary results from June In June, irradiated the same PiN diodes as in May. Measured responsivity with the same LED before irradiation, and found that the annealing did not improve the responsivity compared to that observed after 12 hours of annealing in May. All PiNs were biased and readout online. Observed response from all PiNs, including GaAs PiNs. Estimated degradation of Si PiNs only: –Observed ~50% responsivity after 80 MRads compared to the initial (0 Mrads) responsivity. –Did not take into account degradation of LED due to residual irradiation – preliminary estimation is that optical power of LED went down by ~10% 15

Lifetime test Plan to start the lifetime test of irradiated PiNs at the end of June, as soon as irradiated PiNs will be released from IUCF. Currently have a running test for single channel. Also have ready-to-use setup to test up to 64 channels simultaneously. It is online at Monitor PiNs current and temperature. 16

Summary on tests We developed a simple test stand for PiN responsivity studies, that allows us to avoid packaging. TID passive test shows no degradation in PiN responsivity up to 10 Mrad; Test with protons shows that both S and G are good candidates. They demonstrate 75% of their initial responsivity after 40 Mrad and 50% after 80 Mrad. It would be good to test them at CERN this August with 24 GeV protons and make a detailed comparison. If GaAs PiN diodes survive there will be no need to order a special production of the Si PiN arrays made of S chips. 17