1. Infrared Laser Test System Silicon Diode Testing 29 May 2007 Fadmar Osmić Contents: Setup modifications new amplifier (Agilent MSA-0886) new pulse generator Measurements amplifier tests laser calibration - 241 Am α-source tests on irradiated and non-irradiated diodes

2. Fadmar Osmić – P326 GTK Meeting, May 29 th 2007 -2- Motivation Study the properties of the induced signal in the Si-diode depending on the irradiation level and the laser settings  information for the detector design Reminder: Required time precision ~160 ps per track Measurements on four diodes (3 x 3 mm 2 with 4 guard rings)  reference diode with I det ~13 nA @ 50V and RT  three irradiated diodes: B2: 1x10 12 n eq /cm 2 B11: 3x10 12 n eq /cm 2 B15: 1x10 14 n eq /cm 2

3. Fadmar Osmić – P326 GTK Meeting, May 29 th 2007 -3- Laser Setup New pulse generator and a new high speed single channel amplifier HP 81110A pulse generator used to drive the 1060 nm laser diode: 0.8 ns rise time 4 ns wide pulse  Laser pulse width ~740 ps with a laser pulse rise time of ~570 ps 3 x 3 mm 2 Si-diode with open front-side metallization (pad-side)

4. Fadmar Osmić – P326 GTK Meeting, May 29 th 2007 -4- Modified Laser Setup: Signal generation on the pad side of the diode The distance between the pad and the amplifier is kept as small as possible (~1 cm) in order to reduce noise and reflections

5. Fadmar Osmić – P326 GTK Meeting, May 29 th 2007 -5- Signal shape Reference diode The Agilent amplifier and the new pulse generator allow improved settings of the laser bias pulse: shorter and faster pulses  Laser pulse can be made as short as 0.7 ns Philips amplifierAgilent amplifier Pulse width24 ns4 ns Pulse rise2 ns0.8 ns rise time = 2.80 ns Bias voltage applied 100 V

6. Fadmar Osmić – P326 GTK Meeting, May 29 th 2007 -6- Signal shape With increasing electrical field (bias voltage) in the Si-diode the signal formation becomes faster (i.e. lower rise time) and the amplitude of the induced signal increases. Reference diode Detector bias voltage varied form 10 to 250 V

7. Fadmar Osmić – P326 GTK Meeting, May 29 th 2007 -7- Pulse Area reference diode the pulse area is proportional to the collected charge and reaches saturation after full depletion  around 15 V for the reference diode 20 V

8. Fadmar Osmić – P326 GTK Meeting, May 29 th 2007 -8- Pulse Area diode B15 full depletion around 100 V for the diode B15 before annealing

9. Fadmar Osmić – P326 GTK Meeting, May 29 th 2007 -9- Laser calibration The system calibration was performed using a 40 kBq 241 Am α-source. The α-particle has a mean energy of ~4.2 MeV (~75 mips) and generates a signal with a pulse area of 675.09 ± 13.75 pVs at 100 V bias and RT in the Si-diode of 200 µm thickness. For comparison the laser pulse at optimal settings generates a signal with a pulse area of 546.67 ± 28.38 pVs in the same diode.

10. Fadmar Osmić – P326 GTK Meeting, May 29 th 2007 -10- Conclusions and Outlook Laser test system successfully modified (new amplifier and new pulse generator)  faster and shorter laser pulses possible with ~500 ps rise time Study of the influence of the irradiation on the signal behavior, even during the annealing process Study of the time characteristics of the generated signal Further measurements in the future (P326 RO-chip and 3d- diodes)