"Development of GEM-based Forward Tracking Prototypes for the ILC"

The Center for Applied Physics Studies at Louisiana Tech University is developing prototype tracking chambers based on Gas Electron Multiplier (GEM) technology. This work is an outgrowth of our center’s interdisciplinary GEM development work, which includes faculty with expertise in simulations, fast analog and digital electronics, and nuclear and high-energy physics experimentation. In addition to the chambers under development for the ILC, the center is also constructing a GEM-based tracking detector for the QWEAK experiment at Jefferson Lab, and applying GEM-based imaging technology to biomedical applications.

Please address the following questions in your statement.

The goals of this project include both detector development and testing, and simulation studies. On the hardware front, we seek to develop a triple-GEM tracking chamber with good point resolution, fast readout time, radiation hardness, and low material profile. We will evaluate the applicability of these chambers to the ILC detector environment, concentrating on the intermediate to forward angular regions of cos(theta) roughly between 0.9 and 0.99. Our particular interest in using these chambers as the FCH (Forward Chamber) in the TESLA and initial LDC detector designs.

On the simulations front, we will study the intermediate to forward angular region on the LDC baseline designs, and understand the impact of the TPC endplate on tracking resolution, the necessity of adding an FCH to improve tracking in this region, and the physics requirements for such a device.

Our studies are primarily aimed at the FCH in the LDC detector concept, but could be applicable for similar tracking chamber in other designs.

Currently, Louisiana Tech is the sole institution on this project. We have collaborated in the past with Oklahoma University on general forward tracking studies, and are currently collaborating with Indiana University and members of the SiLC collaboration on tracking studies for LDC.

Among recent work at Louisiana Tech are the construction of a second 10cm X 10cm prototype chamber with improved high voltage routing, gain measurements and studies of QE dependence on ArCO2 gas pressure (the basis for Jena Kraft’s thesis), and simulations of multiple scattering effects in GEM foils (the basis of Narayanan’s thesis). We have also performed simulation studies of the effect of the FCH in the LDC tracking system using the SGV fast simulation program, which were presented at the Snowmass workshop.

In year one of our renewal request, we will build a prototype GEM-based tracking detector using the new 30cm x 30cm GEM foils from3M, Inc. We will carefully test this chamber's performance compared to the 10cm x 10cm prototypes currently being tested, which are constructed with foils manufactured at CERN. We will use our new X-ray test facility, as well as source and cosmic ray testing. The X-ray lab is a new addition to the center, is based on carbon nanotube technology to facilitate pulsing and is capable of delivery 1 kHz of 8 and 20 keV photons. The goal of these tests will be to establish the operational limits of the proto-type device.

We will continue our simulation studies of forward tracking at the ILC. We will use the Mokka front-end to GEANT4 to perform detailed studies of the improvement to tracking with a Forward Chamber (FCH) between the TPC endplate and the EM calorimeter. We will begin studies of different detector readout configurations and begin the process of optimizing the detector design for the GEM tracker FCH. In year two, we will perform beam tests of a prototype tracker module. We plan to install the device at Jefferson Lab’s Hall C which is capable of delivering up to 100 microamps of 6 GeV electrons to a target. This would be preferably in conjunction with a running experimental setup but we could conceivably setup a standalone beam test. The goal of these tests will be to evaluate the operational rate limits of the detector readout system and determine the impact of radiation damage.

In year two, we will finalize a design for the FCH, based on our simulation studies. This should coincide with the timetable for detector conceptual design to be formulated. We will contribute to the conceptual Design of a Large Gaseous Detector for the International Linear Collider, with emphasis on the FCH and tracking in the intermediate to forward regions.

In year three, we will analyze the results of the beam studies. In conjunction with the results of simulation studies, we will then be able to propose a full forward tracking detector for the ILC Large Gaseous Detector, which will hopefully be in the Technical Design stage by this point (year 2006-2007). We will use the pulsed X-ray facility at Louisiana Tech to investigate the effect of ionization chamber and GEM preamplifier wall thicknesses and spacing on pulse rise-time in the GEM.

While we have been successful in testing prototype chambers, a major continuing problem is having sufficient readout electronics. A dedicated readout chip would be a significant help in our chamber studies. We are exploring the development of such a chip with other groups working on GEM-based detectors.

The current level of support, including baseline support for the high energy group and university funds, is barely sufficient to fund the planned activities detailed above. Much time is being lost in training new graduate students, since most of our students are pursuing Masters’ degrees and there is a high rate of turnover. The project could be brought to completion much faster with support for a postdoc, who would be in charge of supervising chamber construction and would also take a lead in simulation studies. As mentioned in the last item, we could also use additional funds for readout electronics.

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Topic revision: 23 Dec 2005, DanPeterson
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