The BRAHMS Ring Imaging Detector is now installed on the Back Forward platform
The picture above shows the radiator volume that contains 878 liters of a mixture of perfluorocarbons at 1.25 atmospheres. In front of the detector and over the entrance window one can see the light tight box for the array of 79 four pixel photomultiplier array and the amplifier cards . The power supply for the amplifiers is located at the top of the rack seen next to the detector.
At the bottom of the radiator volume we installed a pressure transducer. The pressure inside the radiator volume is read through a Keithley KNM-DCV31. This device has an ethernet port with the address: sc3.brahms.bnl.gov
Next to the pressure gauge, a linearized thermistor measures the temperature of the radiator vessel. These two devices are used to monitor any possible gas losses. (As stated in the Lorentz-Lorentz equation, the index of refraction of an ideal gas remains constant if the number of molecules per unit volume is constant)
Once the filling of the radiator was completed, a measurement of the actual index of refraction was performed with a Young's interferometer High voltage for the RICH photomultipliers is supplied by a LeCroy 1458 mainframe (called mainframe B). We use the first eight channels on slot 0. It is expected that at normal running conditions, the high voltage values for all PMTs will be set around -750 volts. Each channel provides voltage bias for 20 photomultipliers, the current drawn from the supply can reach values of some 800 microamps. The hardware limit for module 0 has been set at -900 volts. The following link has a description of previous developement work for the Ring Imaging Cherenkov detector. R.debbe(Updated 8-May-2000)