Mintes of SCT links meeting

                  5 December 1997
                  CERN
                   
                      

    


(1) Radiation Results
(a) John Dowell reported on the analysis of the PIN diode radiation tests.
    The PIN diodes were irradiated to
    1.5 10**14 n/cm**2 Birmingham Dynamitron  
    .7  10**14 n/cm**2 RAL ISIS
    3   10**14 p/cm**2 CERN PS
    The bulk Si PIN diodes essentially dead after fluences greater than 5
    10**13 n/cm**2.
    The eipitaxial Si PIN diodes show a decrease in response of about 30% for
    a fluence of 5 10**13 n/cm**2 but remain constant for higher fluences.
    The dark current rises to 60 nA @20 deg C after the full dose which is
    still very low compared to the signal currents (10 microA).
    Plots of this analysis are arvailable on the web 

(b) Tony Weidberg reported on Dave White's measurements of radiation hardness  
    of DOEIC & LDC. The chips were irradiaited to 6.5 10**13 n/cm**2 at ISIS
    and 3 10**14 p/cm**2. All devices were fully functional after irradiation.
    Low dose rate studies will be perforemd with a gamma source at Birmingham..
    
(2) Bit Error Rate Tests
    Gareth Noyes reported on the status of the bit error rate tests for the
    links. Initially measurements will be made of the BER for data links and TTC links
    separately using either the GEC package with LEDs and slow PINs or the GEC
    package with the fast epitaxial PINs. Tests of two way links will be
    performed when we have the new GEC package with LEDs and fast PINs.
    
(3) VCSEL Tests for TTC distribution
    Tony Weidberg reported on Roy Wastie's results on testing VCSELs for TTC
    didstribution. Roy used a Honeywell HFE 4080 VCSEL in a ST package as a
    replacement for an LED in the Oxford Clock & Control board. A clean 40 MHz
    clock signal was measured with an optical probe (see copy of
    transparencies).
    
(4) Stockholm Optical Links Meeting
    John Dowell reported on the Optical Links Workshop held at Stockholm. 
    Very impressive data was shown by the VCSEL manufacturers on the
    performance and particularly the reliability of these devices. See copies
    of transparencies for more details. Several manufacturers are interested 
    in selling us VCSELs. It was agreed to pursue these VCSEL developments as
    fast as possible and regard the LED option as a fallback.
                 
(5) VCSEL packaging for SCT
    Tony Weidberg reported on plans for (on-detector) packaging of VCSELs for 
    the SCT. Two routes are being pursued:
    (1) MITEL VCSELs in the GEC Silicon package.
    (2) Honeywell VCSELs in a plastic package.  
    See copy of transparencies for more details.
    
(6) SCT Links schedule.    
    A very preliminary schedule was discussed. It was agreed to split the
    project into three sub-projects for planning purposes:
    (1) Develop links for the TSP/Multi-module tests in '98
    (2) Develop the VCSEL solution
    (3) Production, assembly and testing of final cable harnesses.
    More detailed schedules for each of the three sub-projects will be drawn up
    in the near future.
    
    
    (b) ISIS & PS irradiation of LDC & Doric. Dave White
    
(2) Report on meeting with GEC on packaging opto-electronics. Tony Weidberg

(3) Report on Stockholm Optical Links Workshop.  Roy Wastie