Agenda of SCT links meeting 12 November 1998 9 am - 1 pm CERN Bat 104-R-A10
(1) PIN radiation/lifetime tests G. Mahout (2) Radiation tests of truelight VCSELs I. Mandic (3) Radiation tests of Fujikura fibre @ -10C I. Mandic (4) DORIC4 tests D. White/I. Mandic (5) BPM status. R. Wastie (6) DRX specs. D. White/R. Wastie (7) MT Connectors R. Wastie (8) Cross-talk measurements with spearated optics and electronics. I. Mandic (9) Discussion on opto-electronics layout for forward modules. All (10) Plans for radiation/lifetime tests of MITEL VCSELs in Wuppertal I. Maria-Greggor/T. Weidberg (11) Status report from the system test. I. Mandic
Copies of the transparencies are available here
G.Mahout PIN radiation tests
R. Wastie BPM Status DRX Status MT Conenctors
I. Mandic (all talks)
Minutes (1) Gilles Mahout reported results on PIN irradiations. The large drop in responsivity of the PIN diodes reported at the last meeting has been understood as due to an artifact of the scanning machine. The area illuminated was larger than the active area of the PIN and the signal from the region outside the active area is more sensitive to radiation damage. The problem was fixed replacing LEDs with VCSELs and reducing the separation between the VCSEL and the PIN to 500 microns. The decrease in responsivity after irradiation is now measured to be 30-35% in good agreement with earlier results. 96 PINs irradiated to 1.5 10**14 n/cm**2 @ ISIS Of these, sub-sets have had additional radiation 24 have had 2.8 10**14 p/cm**2 @ PS 24 have had 2 10**14 n/cm**2 @ISIS There was no further decrease in response for those PINs irradiated at the PS. The responsivity versus bias curves showed full depletion at around 2V. Studies of possible annealing or anti-annealing effects are underway. The aging tests will start in December. ACTION: investigate feasability of irradiation of a sub-sample to the pixel levels (10**15 n/cm**2). Either at ISIS or Ljubljana. (2) Truelight VCSELs Igor Mandic reported that two Truelight VCSELs were irradiated to 2.3 10**14 n/cm**2 at Ljubljana. There was no change in the IV or LI curves after irradiation. (3) Fibre Irradiation Igor Mandic reported that a sample of Fujikura fibre was irradiated at -15C. No significant attenuation was seen for this fibre or for the sample irradiated at room temperature. A sample will also be irradiated at ISIS to confirm this result. Igor also showed results for the irradiation of the plasma fibre (a candidate rad-tolerant fibre for PPB2 to RODs). One sample showed an anomalously low attenuation. To improve the precision of the measurements, 50m samples will be irradiated to 10**12 n/cm**2 and 10**13 n/cm**2. (4) Igor Mandic showed the first test results with DORIC4. It works with the expected large dynamic range and is not sensitive to exact timing of the clock to data edge (unlike DORIC3). The one problem seen was that DORIC4 can lock onto 20 MHz. This problem can easily be fixed in the final production by reducing the magnitude of one resistor. Dave White has also made functionality measurements with DORIC4 with good results. Dave will start probe tests of chips. After this is done the radiation tests with neutrons and gammas will start. (5) Roy Wastie reviewed the BPM status. Technical problems with the AMS software meant that the October submission was not achieved. These problems are understood now and it should be possible to submit in December. Roy also reviewed the DRX specs (available on the web). There was a discussion of the need for DACS on the DRX. There was a consensus view that we should not put DACs on the first version of DRX. We should use separate DACs for ROD99 and study the need for individual DACs for each channel in the system tests. Only if they were really required should we implement DACs into DRX. Action: discuss this with Maurice Goodrick to check that he agrees to this. (6) Roy Wastie reported that Fujikura will lend us a polishing machine. Roy will use this to make up lengths of patch ribbon fibre and understand the feasibility of doing the MT termination in house. (7) Igor Mandic reported on the results of cross-talk measurements with separated optics and electronics as planned for the forward SCT. Very bad results were found with DORIC3 but very good results could be obtained for DORIC4. ACTION: Tony Smith will make a realistic test with the opto package on a PCB with a connector. This will be used with Pedja Jovanovic's test set-up to measure the effects of cross-talk. (8) Tony Weidberg reported on Wuppertal plans for radiation tests of MITEL VCSELs. They will buy 20 ST packaged MITEL VCSELs and measure their performance before and after irradiation. They will then perform an accelerated lifetime test. (9) Igor Mandic reported the good news that optical links were running successfully in the system tests in Bat 186.