(1) T. Weidberg reviewed the specs for the rad-hard fibre (available
on the web or see the copy of the transparencies. Most of the specs
were standard for a fibre the special ones for our requirements concerned
radiation hardness. Specs were quoted for neutron and gamma doses for levels
applicable to the SCT and pixels.
(2) G. Mahout showed the results of the gamma exposure of the Fujikura
SIMM 50/60/125/250 rad-hard fibre. There was a loss of 1 10**-3 +/- 8 10**-5
dB/Mrad/m which is superior to the specs. It was observed that the fibre
annealed completely when VCSEL light was sent down it.
(3) I. Mandic showed results from the neutron exposure of the Fujikura
fibre. The fibre was exposed to 10**15 n/cm**2 at Ljubljana. The induced
attenuation was 0.12 +/-0.02 dB/m which is much better than the specifications.
No annealing was observed when 1mW of VCSEL light was sent through the
fibre.
(4) R. Wastie had visited Fujikura and discussed problems with MT connectors
and fibre ribbons. It turns out to be simple to split a 12 way ribbon into
two 6 way ribbons as required for the barrel. It is also simple to split
ribbon fibre into single fibres as required for both the forward detector.
(5) A. Nichols showed the SCT fibre routing and the estimated length
of rad-hard fibre. It was decided to allow ~40% contingency on this figure.
(6) K. Einsweiller showed the Pixel fibre routing and the estimated
lengths of rad-hard fibre.
(7) R. Wastie explained Fujikura's comments about our system.
They explained that there would be losses in the coupling between their
SIMM fibre and the GIMM fibre. This was measured to be 1.8 dB. Fujikura
are keen to produce the entire length and claim they could offer a competitive
price for the full length (detector to ROD) of fibre
(8) There was unanimous agreement amongst the SCT groups to proceed
with the purchase, The pixel groups will decide whether to join the order
after their SG meeting next week. There was support for the idea
of purchasing the full length of fibre in rad-hard fibre if there was no
significant increase in cost compared to the two fibre type solution.
It was therefore decided to tender for both the short (detector to PPB2/PPF2)
and long (detector to ROD) lengths of fibre. A. Nicholls will check the
lengths from PPB2/PPF2 to RODs. The tender will be submitted after the
pixel group has decided whether to join the order or not.
For comments, please contact Tony
Weidberg
Last update 11 August 1998