HFRadMon. Status and Performance. A.Ershov, I.Azhgirey, A.Gribushin, A.Kaminskiy, V.Lukanin, L.Sarycheva, O.Sumaneev, V.Pikalov, A.Uzunian 1 HFRadMon. Status and Performance. October 12, 2010

Operation summary System consists of 16 neutron monitors installed on the HF+/HF-, near HF RBX's and near racks with electronics. Data are published by the DIM and DIP server running on cms-hcal-dcs-00 Web-based monitoring client is running on hcaldqm04 Currently data archived in the root files by a client on hcadqm01 Ready to be archived to CASTOR and Oracle DB System does not require DCS, RunControl, DAQ, Trigger etc. In order to operate we need just power and network infrastructure. System is in continuous operation since November 2009 HFRadMon. Status and Performance. October 12, 2010 2

Current status Several detectors were tripping in magnetic field. Three monitors were removed during September technical stop. Electronics has been modified and last Saturday they have been installed back in the UXC. Remaining detectors will be modified in December/January. Until last Saturday all the monitors had 6” dia moderators (Sensitive up to 15 MeV neutrons) For 2 of the detectors (one for each HF+ and HF-), moderator was reduced down to 2” dia. These detectors are supposed to be sensitive to the thermal neutrons. HFRadMon. Status and Performance. October 12, 2010 3

Data Sample All fills after September technical stop. September 22 – October 8, 2010 HFRadMon. Status and Performance. October 12, 2010 4

BSC Collision rate vs HFLumi HFRadMon. Status and Performance. October 12, 2010 5

Detector Sets. The values shown are the neutron rates averaged over detectors in 4 HF areas (HF+/HF-): RBX - area inside shielding near HF RBX's Racks - area outside shielding near electronics racks Detectors used HF- RBX N_MFIT, N_MFIB, N_MNIB HF+ RBX N_PFIT, N_PNIB HF- Racks N_MNXT, N_MFXT, N_MNXB, N_MFXB HF+ Racks N_PNXT, N_PFXB, N_PNXB Calibration and systematic is currently under study → Calibration Factors are not applied. HFRadMon. Status and Performance. October 12, 2010 6

Neutron rates vs HFLumi and BSC Collision rate We use HFLumi for normalization Some indication of dead time effects at high luminosity Need to tune floating prescaling factor algorithm HFRadMon. Status and Performance. October 12, 2010 7

Neutron rates vs Luminosity HF area Slope (1/μb-1/sec) HF- RBX 6.98 ± 0.01 HF+ RBX 1.29 ± 0.01 HF- Racks 0.177 ± 0.001 HF+ Racks 0.119 ± 0.001 HF – RBX rate vs HFLumi Calibration factors are NOT applied. Absolute values may change by a factor of ~2 HFRadMon. Status and Performance. October 12, 2010 8

Neutron rates vs Luminosity (Continued) HF- RBX HF+ RBX HF- Racks HF+ Racks HFRadMon. Status and Performance. October 12, 2010 9

Rates in different HF areas Comparison of the neutron rates in varios HF areas can provide information on Radiation shielding efficiency (Rates “inside” and outside HF shielding – or in RBX and Racks areas). Castor effect :-) (Rates in HF+ and HF-) We examined the following ratios of the neutron rates: RHF-RBX/RHF-Racks and RHF+RBX/RHF+Racks RHF-RBX/RHF+RBX and RHF-Racks/RHF+Racks The next slides don't show errors on these ratios. Statistical precision is good, but without calibration factors applied errors don't make much sense. HFRadMon. Status and Performance. October 12, 2010 10

Castor Effect RHF-RBX/RHF+RBX = 5.5 RHF-Racks/RHF+Racks = 1.5 HFRadMon. Status and Performance. October 12, 2010 11

Shielding Efficiency RHF+RBX/RHF+Racks = 11 RHF-RBX/RHF-Racks = 40 HFRadMon. Status and Performance. October 12, 2010 12

CONCLUSIONS Neutron rates in the HF area show good linearity within a wide range of LHC luminosity Castor on the minus side of the CMS increases the neutron rate in the HF RBX area by a factor of ~5 This value may change once calibration factors are properly applied. The ratios of the neutron rates inside and outside shielding are different on the HF+ and HF- probably due to a fact that HF radiation shielding shadows racks with electronics from Castor. The ratios of the neutron rates in various HF areas do not show dependence on the LHC luminosity. We do not see any significant pile-up of the thermal neutrons yet. This needs to be studied further especially with increase in the LHC luminosity. Detectors with 2” moderators will provide more data for this purpose more points on neutron spectrum ? HFRadMon. Status and Performance. October 12, 2010 13

BackUp slides Absolute calibration, i.e. neutron flux calculation: Count rate Detector specific Coefficient Neutrons/cm2 = Spectrum corr. Anisotropy corr. * * * Correction for a difference between source and real spectra Measured detector rates Correction for a geometrical factor of the detector Measured at the calibration with the Pu-Be source coef. NRM-14 ? ? 14

BackUp slides WdM scan HFRadmon HF LUMI BSC 15