Minutes of Meeting on Background and Radiation Monitoring 6.03.2000 _______________________________________________________________________ Present: J.Stewart, J.Steijger, O.Bouhali, C.Niebuhr, K.Ehret, L.Bauerdick, U.Koetz, W.Zeuner, U.Schneekloth, M.Bieler HERMES -------- The radiation is measured using dosimeters, which are read very month, and 2 Si PIN diodes in the forward region. From April 1997 to March 1998 a dose of more than 65kGy was measured. Some part of the electronics of the MSGC (APC chip) was damaged. Most of the irradiation occurred in one burst in Dec. '97 or Jan. '98. From June to November 1999 70Gy was measured on the outer side. An increase of the leakage current has been observed. Detectors are turned off during injection. H1 ---- Some of the APC chips of the SiVXD were radiation damaged during the machine shifts after the 98/99 winter shutdown. H1 uses RPL glas dosimeters at several detectors close to the beampipe: z(cm) r(cm) detector max dosis (Gy/month) ------------------------------------------------------ -270 5 VLQ 50-100 -38 6 BST 5-50 +/-25 6 CST 5-30 64m 30 FPS 25 There is a strong dependence on both phi and r. The positron beam dump was requested several times. The alarm signal is not yet directly connected to the beam dump. When the tune modulation was turned on 19.01.2000, a sharp background spike caused a broken wire in the CJC. ZEUS ------ Average dose rates measured at the calorimeter are 3-10mGy/day photons and 10-20mGy/day neutrons. The total accumulated dose is 32Gy FCAL, 9Gy RCAL. The BPC suffered radiation damage in 1996 and 1997 (5kGy/month). No radiation damage was observed anymore after modification of the electron beam dump procedure. HERA B -------- The main source of irradiation is expected due to beam target interactions. The estimated dose is 100kGy/year. It is planned to exchange part of the SiVXD every year. No other source of irradiation is expected during normal operation. A concern is accidental opening of the proton collimators and sudden beam movements. Background due the electron beam is not expected to cause any high radiation, although there is not much experience. HERA ------ The new electron beam dump will consist of 3 kickers in the west straight section. The beam will be dumped in a block of copper. The time from the abort trigger to the dump is 400mus. The dump will be triggered by temperature sensors at the new IPs (danger of heating up the vacuum chambers by synchrotron radiation), quench protection monitors at the superconducting magnets at the IPs, RF trans- mitter failures and beam abort signals from the experiments. The RF transmitter failure alarm has to take the probability of a beam loss as a function of beam energy into account. It is not clear whether the beam dump is fast enough to abort the beam in case of transmitter or cavity problems. The time scale of beam losses should be investigated. Uwe Schneekloth