ILC NewsLine
Universities Test Prototype Detectors for an ILC Muon System

The first prototype plane with the 64-element multi-anode PMT (MAPMT) attached to it and the second prototype plane with no PMT attached to it. If you look closely you can see the green light from the 64 fibers coming out of the housing on the second prototype. (Image courtesy of Bob Abrams)

A group of universities in the United States are currently testing prototype detectors that could be used for a muon system in the International Linear Collider. With the help of some high school students from Quarknet, an educational program that brings students and teachers into the laboratories, the University of Notre Dame completed two of the eight large rectangular planes that make up the prototype detector this past summer. These planes are now undergoing tests and collecting cosmic ray data at Fermilab.

Each rectangular plane is made up of 64 strips of plastic scintillator that are 4 cm wide and 1 cm thick. "Each scintillator strip has a groove cut down the middle that has a wave shifting fiber in it", said physicist Mitch Wayne of Notre Dame. "The muon goes through the scintillator, loses energy and a small amount of scintillation light is produced. Some of this light enters the wave shifting fiber and is converted to an optical wavelength -- green. This is then read out in a photodetector. If you see light, you know that a charged particle went through the strip."

Wayne emphasized that the contributions from the Quarknet students had a large impact on delivering the two planes to Fermilab on time. "We had three local high school students working on this project over the summer, and they had a great time", he said. "The Quarknet program is very careful to make sure that the students learn hands-on about particle physics during their internships at the laboratories."

The prototype planes are approximately a quarter of the size of the final planes, which will eventually be 5 meters long and 2.5 meters wide. Fermilab and Notre Dame plan to build a total of 8 prototype planes for testing within the next year. "We need to understand the fundamentals first, and then we will build the full size planes later", said Gene Fisk, a Fermilab physicist.

As opposed to using larger photocathode tubes to detect the light, Fisk and Bob Abrams of the Indiana University are currently testing smaller 64-element multi-anode photo multiplier tubes (MAPMTs that are used extensively by MINOS and other experiments), to which the 64 fibers are connected for signal digitization and readout to a computer. "The window at the end of the tube lets in the light, which strikes a photo cathode, releasing a photo electron", Fisk said. "The electrons get directed, and each one gets multiplied. The 64-element multi-anode photo multiplier tube saves space and is also a cost saving device."

When bench testing is complete on several planes, they will be put into the testbeam at Fermilab. "In the test beam, we want to understand how often we get a fake muon", Fisk said. "We will shoot in a pion and measure the number of times it looks like a muon. The muons shouldn't make hadronic showers. This measurement will be used to determine efficiency and purity for the muons."

Other universities/institutes involved in the ILC muon system R&D effort around the world include: University of Colorado, Colorado State Univ.,UC Davis, INFN Frascati(Italy), Kyungpook Nat'l Univ. (Korea), Northern Illinois University, Shinshu Univ.(Japan), Wayne State University, University of Wisconsin.

--Elizabeth Clements