From: Peter R Hobson [Peter.Hobson@brunel.ac.uk] Sent: 23 October 2003 13:22 To: Tejinder.Virdee@cern.ch Cc: Robert Brown; Cockerill, DJA (David) Subject: RE: SLHC Jim Here are my thoughts, I'd like to be able to spend more time on the details, but since your deadline is so very tight this is the best I can do at present. Please note I have NOT considered the new front-end electronics, I assume that you will consult Jordan Nash for that, nor the end-cap crystals (LeCoq and Huhtinnen). I hope that David C (+ Bob?) can quickly look at this to see if I have said something completely stupid! Peter ------------------------------------------------------------------------- hep-ph/0204087 clearly and correctly identifies the key components of the end-cap which will be at risk from the factor of ten increase in yearly luminosity. We should presume that existing components, such as the vacuum photodetectors, at the worst region (eta = 3.0) will have had a dose of order 10 kGy by the start of SLHC in 2013. Based on our tests so far, the damage to the current VPT due to gamma induced faceplate darkening is showing signs of saturation at 20 kGy so an optimistic scenario would suggest that prehaps we already have a glass which will be tolerant enough for the SLHC. This assumption must of course be thoroughly tested. A new Russian glass (C96) which shows even greater tolerance to neutron and gamma irradiation has been developed and evaluated and a small number of operation vacuum phototriodes have been built with it. The lifetime under high current operation with this new glass has not been determined. Recent work (unpublished, but presented at ICATPP8, October 2003) from the INTAS project on ultra-radiation tolerant VPT development suggests that the induced noise from direct neutrons hitting the VPT might be a concern. At the maximum flux predicted for the inner edge of the end-cap we estimate that the additional noise for normal high luminosity LHC running is of the order of the intrinsic front-end amplifier noise. Presumably this would now increase by about a factor of ten and thus make a noticable difference to the energy resolution in the end-cap calorimeter. The induced noise from gammas will remain negligible. A major concern is the low-capacitance co-axial signal cable connecting the VPT to the front-end electronics. Already we have a challenge to find a commercial cable with the correct electricaland mechanical properties which will withstand the normal 10 year LHC dose. I anticipate that this is an area where R+D will be required. The same problems are also likely to occur with our COTS connectors and HV filter components. Our tests on structural materials (C-fibre alveolars and their glue join to the aluminium supports) were carried out to doses as high as 5 MGy with no adverse effects. > > As per our conversations I would be much obliged if you could send (by > tomorrow evening) some text and some numbers on the three phases for > upgrading to run at the SLHC concerning your sub-detectors. Funds needed for R&D --- We would need to identify, and possibly develop, new signal cables. We would need to identify COTS HV capacitors and resistors We would need to verify the radiation effects on our existing known glass faceplates (UV borosilicate and the C96) up to the new dose limits. I imagine this area might need of order 3 Staff-years and £50k to £100k for components, cost of facilities and (in particular) the possible costs of developing new cables and connectors. prototyping ----------- Funds may be needed for prototyping of VPT (of existing design) with the C96 glass faceplates (only a few have been mae so far). New prototype cables and possibly new HV filter cards to be produced This might require 2 Staff-years and £50k (mainly for a pre-production batch of VPT with new glass faceplates). construction ------------ I assume you should get these details from Dave C! ******************************************************** Dr Peter R Hobson Reader, Department of Electronic and Computer Engineering Brunel University, Uxbridge UB8 3PH G.B. Telephone: (0)1895 203203 FAX: (0)1895 272391