University of Iowa Cerenkov light test

摘要

This Memorandum of Understanding requests beam time at Fermilab during the Winter 2005-2006 Meson Test Run to measure the signal size from various configurations of Cerenkov light generators and phototubes. The University of Iowa has pioneered in application of Cerenkov radiation for high-energy detectors. One of the results of this effort is the huge forward calorimeter for CMS (at the LHC) with a half million quartz fibers in iron. The laboratory plans to use this expertise to develop a variety of detectors making use of Cerenkov light and phototubes as the active elements in calorimeters for high-energy particles. There are three immediate applications related to forward angle calorimeters in CMS; ZDC, CASTOR, and the HE upgrade. The University of Iowa will make the detailed design for the Zero Degree Calorimeter. The proposed design uses tungsten plates interleaved with sheets of quartz fibers. In the EM part the plates are perpendicular to the beam, in the rear hadronic part they are at an angle of 45{sup o}. Because of the limited cross sectional area of the plates, there will be considerable leakage of shower particles out of the four sides. We plan to measure this leakage and compare the results with simulations. The leakage will be measured by placing a polished aluminum tank, 4 in wide, 20 in long and 8 in deep on top of absorber material made of blocks of tantalum and copper. The fluid in the tank, that generates the Ccrcnkov light, could be water; but ethylene glycol (antifreeze, but without the added color) would be better. Being non-polar, it is not corrosive like water, and it has a higher index of refraction, 1.42 vs. 1.33. The larger index of refraction would result in more Cerenkov light and better coupling to the PMT. The University of Iowa has been asked to design the light guides for CASTOR that take the light from the quartz plates, in which the light is produced, and carry it to the PMTs. These plates, interleaved with tungsten plates, are oriented at 45{sup o}. The University of Iowa has been asked to consider methods for replacing the scintillators in the HE hadronic calorimeter with quartz plates, which will not be harmed by the high radiation levels expected with the proposed LHC upgrade in luminosity. The success of this project depends on finding an extremely effective way to couple the Cerenkov light into wave-length shifting fibers. These various configurations can all be simulated to some degree, but it is essential that the simulations be accompanied by laboratory tests. In most cases 120 GeV protons will be adequate, but in some cases there will also need to be tests using 8 and/or 16 GeV electrons. For all of the tests, the setup will be small, at most only a few cubic feet. There will be no gas supply or complicated mechanical devices. The active devices will be a few PMTs. The overall project will consist of a number of short, simple experiments, each lasting from one to three days. The MTB is an excellent facility for such tests.