SCTlinks

Radiation Hardness of Fibres and Connectors

  1. Rad-hard fibre . Masurements of radiation hardness to neutrons of the multi-mode fibres we propose to use have been done by the Liquid Argon Calorimer Links group. They have exposed the Fujikura SIMM 50/60/125/250 fibre to 2 1014 neutrons/cm2 and find a loss of about 1dB/100m See ATLAS LARG-No-002 for details. A measurement of the radiation hardness of the Fujikura fibre to a fluence of 1015 n/cm2 (+/- 20%) has now been performed. Within the precision of the measurements, no significant radiation induced attenuation was obserevd. The results for irradiation at room termperature and cold (-10oC) are summarised below:
    1. at +20oC: loss = - 0.03 +/-0.01 (stat) +/- 0.03 (syst) dB/m
    2. at -10oC: loss = -0.01 +/- 0.01 (stat) +/- 0.03 (syst) dB/m
    We conclude that there is no significant difference between the cold and warm irradiation of the Fujikura fibre.The radiation hardness to neutrons is at least an order of magnitude better than required.

    Measurements of radiation hardness to gamms has been carried out at Birmingham with a Co60 source. The results show that the Fujikura fibre is sufficiently radiation hard to survive the 30 MRad dose expected in the wost area of the Pixel detector. The plot from these measurements is available here. The Fujikura fibre is therefore believed to be sufficiently radiation hard for the use by both the SCT and the Pixel detectors. This fibre will be used from the detector modules to the RODs. This fibre has now been purchased. The radiation tests from the samples from the first three preforms are available here.

  2. Rad-tolerant fiibre.   we are investigating the use of a GIMM 50/125 micron fibre for use between PPB2/PPF2 patch panels and the RODs. The results for the radiaion hardness of this fiibre are shown in the plot which gives the attenuation vs dose for 100m of this fibre.  The radiation hardness for neutrons has also been measured and the results of this analysis are sumaries in the plot of attenuation vs fluence.  While it is clear that this fibre is not sufficiently radiation hard for use inside the inner detetcor it  probably can be used from the patch panels to the RODs (this will not be used for the SCT but is still an option for the Pixel detector).
  1.  Connectors.CMS have measured the radiation hardness of MT connectors and found good results.
A draft of a NIM paper on fibre radiation hardness is available (postscript file).
Send comments about these pages toTony Weidberg