MRI: Development of Calorimeter Prototype Modules for the...

Development of Calorimeter Prototype Modules for the ILC Test Beam Program

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MRI: Development of Calorimeter Prototype Modules for the International Linear Collider Test Beam Program

Jaehoon Yu1, Andrew Brandt1, James Brau2, Kaushik De1, Gary Drake3, Ray Frey2, José Repond3, David

Strom2, David Underwood3, Arthur Wicklund3, Andrew White1 and Lei Xia3

1. Department of Physics, The University of Texas at Arlington, Arlington, TX 2. Department of Physics, The University of Oregon, Eugene, OR

3. High Energy Physics Division, Argonne National Laboratory, Argonne, IL 1. Prior NSF Results Within the Last Five Years Jaehoon Yu: University of Texas, Arlington. EIA-0216500 “Acquisition of High-Performance Computing and Information Storage Infrastructure at UTA,” 9/1/02–8/31/05, $950,000. UTA constructed a computing facility along with high storage capacity for collaborative and multi-disciplinary research at UTA and the University of Texas Southwestern Medical Center. Brought online in late 2003, the UTA high energy physics group has turned this facility into the first large U.S. DØ Regional Analysis Center outside Fermilab. The computing power at the facility has been fully utilized since then. It produced several million DØ MC events and became one of the most significant contributors to the ATLAS Data Challenges. The complex is also used for an interdisciplinary grid computing course at UTA (CSE 6350). Andrew Brandt: University of Texas, Arlington. PHY-0320554 “A Consortium for the Acquisition of Equipment to Complete a Proton Detector for the DØ Experimental Particle Physics Program,” 8/1/03–8/1/05, $90,209, sub-award from Northern Illinois University. The majority of these funds have been used to complete the DØ forward proton detectors, which are currently taking data. James Brau, Ray Frey, David Strom: University of Oregon. PHY-0071058, 9/1/00-8/31/03, $490,000, and PHY-0245109, 9/1/03-8/31/06, $510,000, “A Search for Gravitational Radiation at LIGO”. These awards support the involvement of the group in the LIGO Scientific Collaboration (LSC), primarily providing salary and support for students and post-doctoral researchers. The Oregon contributions have primarily been in the areas of instrumentation for environmental influences on LIGO, analysis of these influences, and searches for burst sources of gravitational radiation and development of associated techniques, especially where the burst sources are associated with external signals such as those from gamma-ray bursts. 2. Introduction

This document proposes a joint effort between the University of Texas at Arlington (UTA), the University of Oregon (UO), and Argonne National Laboratory (ANL) to develop and construct three prototype calorimeter modules to be used in a test beam program [1] for International Linear Collider (ILC) detector research and development. This proposal is a critical step in a linear collider detector development, as it will fund the instruments for testing of leading technologies for ILC calorimetry, and also provide invaluable results on hadronic shower development with a highly granular readout. The consortium assembled in this proposal is exceptionally qualified for this effort. The group is led by Jaehoon Yu (UTA), who is leading the worldwide Linear Collider testbeam effort, and along with Andrew White (UTA) has played a major role in developing one of the most promising digital hadron calorimeter (DHCAL) technologies (Gas Electrom Multiplier, GEM). Ray Frey (UO) is a leader of the American ILC calorimetry group and is heading Si-W electromagnetic calorimetry (ECAL) development. José Repond (ANL) is also a leader of the American ILC calorimetry working group and has been leading the development of another promising DHCAL technology (Resistive Plate Chambers, RPC). All of these groups have been receiving modest R&D funding from the DOE LCRD, ADR and other programs, and have made dramatic progress in these areas over the past two to three years. However, the next step forward will require the significant funding requested in this proposal for a prototype to be used in a test beam. To make the test beam possible, in addition to the three participating institutions, Fermi National Accelerator Laboratory, Stanford Linear Accelerator Center, University of Iowa, University of Chicago, Boston University, University of Iowa and University of Washington are contributing to this project.


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The funds requested in this proposal will allow the consortium to develop and construct a 30-layer Si-W ECAL with its front-end readout and two 40-layer, 1 1 1× × m3, DHCALs with the two most promising active medium technologies along with their corresponding front-end electronics. These instruments will provide the opportunity to test three new calorimeter technologies for ILC detector design along with data on hadronic showers with an unprecedented granularity for significant improvement in algorithms and in detector simulations. Numerous graduate and undergraduate students will have opportunity to participate in frontier detector technology research and development. A large number of publications will result from the development and construction of these instruments and from the results of the subsequent beam tests. 3. Research Activities High Energy Physics Research. Advances in High Energy Physics (HEP), which is concerned with a fundamental understanding of forces and the constituents of matter, require the ability to probe progressively smaller distance scales. These small scales are accessible through the study of interactions between particles at very high energies. While very high–energy particles can be obtained from natural sources in the universe, their intensities are too small to provide the necessary precision for detailed studies. To obtain the statistical precision necessary for discoveries at high energies, particle accelerators are required. The next such machine, ILC, will collide electrons and positrons in an energy range of 500 to 1000 GeV and will operate at high luminosities.

To fully exploit the physics potential of the new accelerator, detectors capable of studying the details of the products of high-energy collisions and disentangling and deciphering complex signatures are required. The detectors must be capable of measuring jets of hadrons with excellent energy and angular resolutions, a critical requirement for the discovery and characterization of the postulated Higgs bosons and super-symmetric (SUSY) particles. Since calorimeters measure the energy of particles and provide information for particle identification, they play a crucial role in any experiment at a particle collider.

Linear Collider Research. Detectors at the International Linear Collider (ILC) are envisioned to be precision instruments that can measure Standard Model physics processes at the electroweak energy scale and discover new physics processes in that regime. In order to take full advantage of the physics potential of the ILC, the performance of the system of detector components comprising an experiment must be optimized, often in ways not explored by previous generations of collider detectors. In particular, the design of the calorimeter system consisting of electromagnetic and hadronic components demands new approaches to meet the precision required to accomplish the physics goals. As a precision instrument, the calorimeter

Figure 1. Comparison of the shower radius in a hadronic calorimeter as predicted by fifteen different MC models of hadronic showers normalized to G4-FTFP. Differences from a few percentto as large as 60% between different models can be seen for a given technology of the sensitive gap.


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will be used to measure jets from decays of vector bosons and heavy particles such as the top quark, Higgs boson, and SUSY particles. At the ILC, it will be essential to identify and distinguish the presence of a Z or W vector boson via their hadronic decay mode into two jets, requiring a dijet invariant mass resolution of about 3 GeV or, equivalently, a jet energy resolution of ~ 30% (GeV)E Eσ . None of the calorimeters in existing collider detectors have been able to achieve this level of precision. Requirements of Calorimeters. In order to improve jet energy resolution to meet the necessary precision requirements, new methods and technologies must be explored. The Particle Flow Algorithm (PFA) builds on the energy flow algorithm [2] pioneered by the ALEPH experiment [3] at LEP [4] to reconstruct hadronic jets. In this algorithm, the relatively superior resolution of the tracking system is exploited by replacing the measured calorimeter cluster energies with the measured momenta of the associated charged tracks (~60 % of the jet energy). The electromagnetic calorimeter is used to measure photon energy (~25% of jet energy). Both electromagnetic and hadronic calorimeters are used to measure the energy of neutral hadrons (~15% of jet energy). In order to optimally use a PFA, one must avoid double counting corrections that were necessary for the LEP–era detectors [5]. This requires fine lateral and longitudinal calorimeter segmentation and a high spatial resolution tracking system to precisely identify the three different components of a hadronic jet. The optimization of the calorimeter designs for the application of PFA is critical to accomplish the physics goals of the ILC. The fine segmentation of the calorimeter requires a large number of readout channels, leading to the consideration of a simple one-bit readout for the hadronic calorimeter. Research on the Behavior of Hadronic Showers. Development of PFAs relies heavily on Monte Carlo (MC) models. At present, a number of different hadronic shower development models [6 – 9] exist. These models differ significantly in several important aspects. Figure 1 shows a comparison of average predicted shower radii for 15 different MC models of hadronic showers [10]. Differences up to 60% are seen. Presently, however, insufficient experimental data exists to distinguish between these models. To remedy this situation a large part of the planned test beam program, which utilizes the instrumentation constructed through the support of this proposal, will be devoted to the detailed measurement of hadronic showers, allowing for the improvement and validation of these models. Research on New Calorimeter Technologies. The design of a precision calorimeter for the ILC detector requires the development and testing of new detector technologies. The funds from this proposal will allow for the design, development and construction of prototypes of three different calorimeter technologies: a silicon-tungsten (Si-W) ECAL [11] and hadronic calorimeters (HCAL) based on Resistive Plate Chambers (RPC) [12] and Gas Electron Multipliers (GEM) [13]. The analog ECAL will have 0.5 cm 0.5 cm× lateral segmentation and employ novel electronics to keep the active gap size at 1 mm. The signals will be read out with high resolution. The HCALs will feature cell sizes of 1 cm 1 cm× and will be read out with one-bit resolution (digital technique). Calorimeters featuring these technologies have never before been constructed on a large scale. Thus, these prototypes will provide the first opportunity to test these novel technologies in a beam environment. Simulation studies showed that the energy resolution for neutrons and K0 with digital readout is comparable to the results obtained with analog readout [14–16].

Research and Student Training. Given the opportunities provided by the frontier detector technology development contained in this proposal, we anticipate involving many physics and engineering undergraduate students in all phases of the three projects. We also anticipate student training for Masters and Ph.D. students in physics and engineering, through their participation in design, simulation, prototype construction, commissioning, data taking, as well as the analysis of the collected data. Table 1 summarizes the anticipated number of personnel who will be using the instrumentation developed through this project.

Categorization Number of Personnel Senior Personnel 20 Post-doctoral Fellows 8 Graduate Students 16 Undergraduate Students 30

Table 1. List of personnel to use the research instrumentation constructed in this proposal.


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Sources of Support. The funds requested in this proposal will provide material costs for development and construction of the three calorimeter prototypes. The engineering and personnel support will be provided by the institutions participating in this proposal, other contributing universities, and two national laboratories, Fermi National Accelerator Laboratory (FNAL) and Stanford Linear Accelerator Center (SLAC). Table 2 summarizes the sources and the types of support complimenting this proposal. Significant engineering and development manpower will be provided by the three national laboratories. The participating institutions will provide manpower for the local design effort, pre-prototype testing, assembly of the final prototype modules and commissioning of the modules at the test beam facility through funding sources outside of this proposal. The funds requested in this proposal will serve to acquire the material for development and construction of the three prototype modules and their readout systems

4. Description of Research Instrumentation and Needs Implementing the PFA concept requires a dense, highly segmented ECAL to measure the energy of

electrons and photons and cleanly separate their energy depositions from those of hadrons. A highly segmented HCAL is also required to resolve the energy depositions due to charged hadrons from those due to neutral hadrons. The transverse segmentation necessary to carry out particle flow is on the order of 5 mm 5 mm× for the ECAL and 1 cm 1 cm× for HCAL [11] for a linear collider detector and for the test beam program [1]. The Moliere radius (a measure of the shower size) of the ECAL must be kept small, while energy resolution considerations for electron and photon final states requires approximately 30 longitudinal samples [17].

Considering only the energy measurement error for each particle in the PFA, the contribution to the energy resolution from charged hadrons in a hadronic jet is completely negligible, since their energies are replaced by the momenta measured in the tracking system. The contribution from photons is comparatively small since these are generally well behaved and measured. Thus the dominant contribution stems from the neutral hadrons. A

nE/50.0 single neutral hadron energy resolution leads to an intrinsic best jet energy resolution of 0.15 ~ 0.20 jetE . This resolution is further degraded due to imperfect separation of the energy

deposits in the calorimeter and their incorrect assignment to charged or neutral particles. This additional ‘confusion term’ is estimated [18] to be the dominant contribution to the jet energy resolution of 0.3 ~ 0.4 jetE . This corresponds to more than a factor of two improvement over LEP II detectors [19, 20].

Sources of Support Types of Support

University of Texas at Arlington

Engineering for design, source and cosmic-ray testing of prototypes, construction manpower of GEM based HCAL and joint development of gas-calorimeter readout electronics

Argonne National Laboratory

Engineering for design, source and cosmic-ray testing of prototypes, construction manpower of RPC based HCAL and joint development of HCAL readout electronics

Institutions requesting support in

this proposal

University of Oregon Design and testing of prototypes, construction manpower for Si-W ECAL and readout electronics development and testing

Fermilab Engineering for design and joint development of gas-calorimeter front-end readout electronics

SLAC Engineering for design and joint development of Si-W EM calorimeter front-end and DAQ electronics

University of Iowa High Voltage System design and testing; Gas distribution system design and testing, design and testing of partial HCAL electronics

Univ. of Chicago Design and testing of partial HCAL electronics and beam tests Boston University Design and testing of partial HCAL electronics and beam tests

Institutions NOT

requesting support in

this proposal

Univ. of Washington Design and testing of partial HCAL electronics and beam tests

Table 2. List of sources and types of supports to this project, not included in the budget request.


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Since the pattern recognition element is a crucial factor for the design of ILC calorimeters, the behavior of hadronic showers must be understood in full detail. To date, measurements of hadronic showers with a fine spatial resolution have not been accomplished, hence the need for a much improved description. Thus, one of the primary scientific goals of the test beam program to be achieved with the instrumentations from this proposal is to measure hadronic showers with unprecedented spatial resolution. The three calorimeter prototypes developed and constructed through this proposal will be used to accomplish these goals. Since a test beam cannot produce jets, our approach will be to tune the existing simulation codes over the range of single particle energies expected in jets produced at the ILC, and then to optimize the detector designs using these validated codes.

We are proposing a radically new approach to the measurement of jet energies and jet-jet masses, using new technologies. The need to ensure reliable operation of a digital calorimeter system over an extended period at the ILC also requires that we have critical information available before the final technology selection. For these reasons we will build three prototypes, one ECAL and two DHCAL’s. The use of GEM and RPC for the DHCAL’s are new in the field of calorimetry. As such it is essential that both of these be tested to determine performance characteristics and reliability of operation, over an extended period, with respect to stability of construction, efficiency, multiple hits, material degradation, gas flow rates, temperature and humidity effects and beam exposure (C/m2). The extension from the present small prototypes to 400,000 channel systems will provide the confidence to make the final technology selection. Silicon-Tungsten (Si-W) Analog Electromagnetic Calorimeter (UO). The requirements of a dense, highly segmented calorimeter have resulted in the choice of tungsten layers sampled by segmented silicon detectors as the leading candidate for the ECAL. The small Moliere radius of tungsten (9 mm) gives compact photon showers which are more easily separated from charged hadrons. At the same time, the interaction length for hadrons is relatively large for tungsten, providing higher longitudinal separability between photons and hadrons. Silicon detector wafers are readily segmented and provide adequate signal charge with a thin sampling material [21]. The main questions for this technology are cost which will probably become reasonable in the ILC timescale and the ability to handle large number of readout channels, which requires a sensible integration scheme.

In 2002, UO proposed a Si-W implementation detailed below provides an integration of silicon detectors with readout which is necessary for a realistic ILC detector. The design can provide the required transverse segmentation while maintaining the small tungsten Moliere radius by minimization of the readout gap (about 1 mm). The silicon layers are tiled with detectors which are the size of a large silicon wafer (presently 15 cm diameter). Each detector consists of ~1000 individual pixels, nominally 5 mm across, which are connected to a single readout chip (ROC), which is bump–bonded onto the detector wafer, as depicted in Fig. 2. The individual pixel signals are brought to the ROC by lines metallized directly on the wafer. The ROC is an ASIC [22] which provides full analog and digital signal processing for each pixel. It requires only ~10 external connections for serial digital output, power, and control. The ROC is placed in a cutout in the G10 motherboard, as indicated in Fig. 3.

Figure 2. 1000-pixel silicon detector (left) with the position of ROC in blue and a schematic diagram of one channel of ROC.


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Some key features of the design include: 1) cost and complexity are largely independent of transverse segmentation, down to 2 mm; 2) the readout gaps can be kept small, ~1 mm (see Fig. 3), maintaining the excellent Moliere radius of tungsten. The effective Moliere radius increases only to 13 mm compared with 9 mm for pure tungsten. A reduced Moliere radius directly impacts detector cost, since a calorimeter placed at smaller radius can achieve similar performance; 3) only passive cooling within the main structure is foreseen to be necessary, thus allowing a simple and hermetic ECAL; and 4) charge measurement over the full dynamic range is readily attainable. (A 500 GeV electron produces a signal at shower maximum of up to 2500 MIPs in a 5 mm pixel). While we are presently considering the implementation of this design concept in the context of the compact, dense SiD detector [23], it is easy to imagine applying it to other designs [24, 25], if cost were manageable.

Given these features, in a nominal design, the first stage of the ROC requires a large (10 pF) feedback capacitor to handle these large signals. However, typical signals are much smaller, and, in fact, we require that MIPs are measured with a good signal-to-noise ratio (SNR). A large feedback capacitor makes this a difficult prospect. We have developed a potential solution to this difficulty, as indicated in Fig. 2. The feedback capacitor is dynamically switched from a nominal small value to the large one only in case of a large signal. This improves the SNR after the first stage.

The largest power consumption is in the front-end of the ROC. The time structure [22] of the ILC allows this portion to be switched off between pulse trains (which nominally arrive at 5 Hz repetition and are of duration 1 ms). The average power dissipated in the ROC based on the engineering simulation is 10 mW. This is well below the 40 mW threshold we estimate at which passive cooling does not suffice. We plan to draw the heat out of the modules along the tungsten radiators to cooling loops provided at the module edges (behind the ECAL). We have taken into account settling times in the electronics due to this power cycling.

An excellent vendor with competitive prices for tungsten absorber plates has been located. They are able to supply tungsten sheets of the desired thicknesses with essentially any sensible alloy composition. They can make these sheets long enough to span the width of an assembled module in a full ECAL. This is significant, since this allows for the possibility that the tungsten alone will suffice to conduct the ROC heat load to the edges of the modules (see below). A sufficient number of tungsten plates for a 30-layer test beam module have been purchased.

The funds requested in this proposal will allow us to purchase 50 silicon detectors for the 30-layer test beam ECAL module. We would include several modifications to the original prototypes [26] to fit the detectors for a test beam. The original prototype characterizations in the lab were quite satisfactory. GEM-Based Digital Hadron Calorimeter (UTA). This approach is based on the use of gas electron multiplier (GEM) [13] foils to achieve amplification of the electrons released in a gas by the passage of a charged track. A GEM foil consists of a 50 µm layer of Kapton clad on both sides by 5 µm layers of copper. The 70 µm diameter holes are etched through the three layers and have a spacing of 140 µm. The

Figure 3. Readout gap concept for Si-W ECAL. The readout chip (ROC) is bump bonded to pads metallized onto the silicon detector wafer.


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amplification results from the acceleration of electrons in the high electric field created in the holes in the GEM foil, providing an avalanche through the subsequent collisions with argon atoms in the gas.

UTA has been working on GEM-based DHCAL for the past three years. We have carried out simulation studies of the performance of a digital hadron calorimeter based on GEM technology. The simulation contained a detailed representation of GEM active layers with energy deposition and threshold application for the digital studies. Figure 4(a) shows single pion energy resolutions for GEM DHCAL (green) which is comparable to the TESLA TDR [18] detector (red) except at low energies. Figure 4(b) compares the jet energy resolution for GEM DHCAL using PFA (blue), which has a sampling term of 30%/√E [16], to other detector technologies and techniques, using the single pion energy resolution. This study clearly demonstrates the potential of PFA with GEM DHCAL to achieve the excellent jet energy resolution required by the physics program at the ILC.

Figure 5(a) shows a schematic of the UTA prototype double GEM detector. The ionization signal from charged tracks passing through the drift section of the active layer is amplified using multiple GEM foils. The amplified charge is collected at the anode, or readout pad layer, which is at ground potential. This layer is subdivided into the small1 cm 1 cm× pads needed to implement the high granularity digital approach. The potentials required to guide the ionization are produced by a resistor network, with successive connections to the cathode, both sides of each GEM foil, and the anode layer. The pad signals are amplified, discriminated, and a digital output produced in each local region of the detector. The GEM design allows a high degree of flexibility for variable pad sizes as required by the specific application. Figure 5(b) shows a schematic view of a section of a GEM-based digital calorimeter.

In order to gain experience with GEM detectors, and to develop ideas for their application to digital calorimetry, we have built and operated several configurations of prototype detectors [27], using 10 cm 10 cm× GEM foils purchased from the Gas Detectors Development (GDD) Group at CERN [28]. Figure 6(a) compares a typical signal amplification measured from our chamber to CERN results [29]. We have been working in two main areas: the mechanical aspects of large GEM-layer assembly, and the fabrication of large area GEM foils. The layer assembly has required development of tools to handle large area foils, and present them flat for integration into a detector. We have also developed initial components for the detector walls (1 mm and 3 mm heights are required), gas in/outlets, and spacers to maintain the separation of the foils. We have also looked into the effects of changing the proportion of Argon in our Argon-CO2 gas mixture. We find that we obtain a factor of three increase in signal size changing from a 70/30 mixture to an 80/20 mixture. The latter mixture has given very stable detector performance over weeks of operation with no discharges. We therefore expect minimum signal sizes for MIPs in the range 15–

Figure 4 (a) GEM DHCAL single pion energy resolution. (b) GEM DHCAL jet energy resolution using a PFA.


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20 fC using the 80/20 mixture; minimum signals in this range ease the design of the front-end ASIC described below.

The goals of this proposal require the development of large GEM active layers to construct a 1 1 1× × m3 calorimeter prototype for a test beam. We have been working with 3M Corporation-Microinterconnect Systems Division, Austin, Texas, to develop 1 m 30 cm× foils. Figure 6(b) shows a roll of small circular GEM foils produced for another application [30], and Fig. 6(c) shows a view of the 3M reel-to-reel production process. As a step towards these full size foils to be purchased through the funds requested in this proposal, we will soon purchase a batch of 30 cm 30 cm× foils to use in the assembly of a stack of five double-GEM detectors for a cosmic ray exposure to study cell efficiency, hit multiplicity, and tracking efficiency. This cosmic ray prototype will be constructed through R&D funds at UTA.

We also have been developing the assembly techniques needed to create full-size layers. We have developed techniques for holding the foils flat prior to assembly, providing the necessary gas-tight walls of 1 mm and 3 mm height, providing spacers to maintain the 1 mm and 3 mm foil separations across the entire area of the foils, and for providing unobstructed gas flow. We use a 2 mm slice of the absorber steel as a “strongback” on which to assemble the GEM active layer, and guarantee layer flatness. The budget

Figure 5 (a) A schematic diagram of a double GEM sensitive gap structure. (b) A schematic diagram of a partial stack of a GEM DHCAL.

Figure 6 (a) Triple (TGEM), double (DGEM) and single GEM (SGEM) gains as a function of electric potential applied in the gap. The cross indicates the measurement from the UTA DGEM chamber. (b) A picture of 3M produced GEM foil for tracking systems. (c) A picture of a 500 ft role of a flexible circuit in production.


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requested in this proposal will allow us to purchase sufficient area of GEM foils to construct 50 active layers for the test beam prototype.

For the readout of the GEM signals, we have been co-developing ASIC electronics [31] to be shared for both GEM and RPC technologies. The ASIC will have a switchable gain, allowing high gain for the smaller GEM and low gain for the larger RPC signals. For the 1 1 1× × m3 calorimeter test beam prototype module, we will use the same 9-layer PC-boards, with the ASICs mounted on them, as for the RPC-based module. RPC-Based Digital Hadron Calorimeter (ANL). Resistive Plate Chambers (RPCs) with small readout pads appear to be an ideal candidate for a hadron calorimeter designed to optimize the application of PFA. They can provide the segmentation of the readout pads of the order of 1 to 4 cm2, which is necessary to keep the “confusion term” [18] small, and they can be built to fit small active gaps (less then 10 mm) to maintain a small lateral shower size. Glass RPCs have been found to be stable in operation for long periods of time [32, 33], especially when run in avalanche mode, and the rate capabilities are adequate for the Linear Collider and for test beam studies of hadronic showers. RPCs are inexpensive to build since most parts are available commercially. The readout electronics can be simplified to a one-bit per pad resolution. Signals in avalanche mode are large enough to simplify the design of the front-end electronics.

Figure 7 shows a schematic diagram of a single-gap RPC. The chamber consists of two plates with high electrical resistance. Readily available window glass of thickness 0.8 to 1.1 mm will be used to construct the RPC. High voltage is applied to a resistance coating on the outside of the glass plates. The resistance of this coating must be low enough to re-charge the glass locally after a signal hit, and high enough to allow the electric field of the electron avalanche in the gas to reach the external signal pick-up pads. The glass plates enclose a gas volume in which ionization and electron multiplication takes place. Particles traversing the gas gap ionize the gas, creating an avalanche of electrons drifting towards the glass plate at positive high

Figure 8. Hit multiplicity versus detection efficiency measured with RPCs at different operating voltages.

Figure 7 Schematic diagram of a typical Resistive Plate Chamber.

Signal

Graphite

Resistive platesGas

Pick-up pads

HV


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voltage. The signal is picked up inductively with pads located on the outside of the glass. Work on developing RPCs for application in a hadron calorimeter has been underway for the past two to

three years at Argonne National Laboratory [34]. A number of single- and multi-gap chambers have been built and have been tested thoroughly with sources and cosmic rays [35–39]. Tests with single pads of 10 x 10 cm2 or multiple pads (up to 64) each with the size of 1 cm 1 cm× have been performed. The multipad tests were performed with a 64-channel readout system based on VME, designed and built specifically for these tests. The tests included measurement of the signal charge and MIP detection efficiency as a function of high voltage, comparison of different gas mixtures, measurements of the hit multiplicity versus efficiency, the noise rate, the signal characteristics as a function of capacitance to ground of each pad, the mechanical properties of the chambers, the rate capability, long-term stability, and comparisons of different chamber designs (multi-gap chambers, chambers with only one glass plate, chambers with high and low resistivity coating). Figure 8 shows the hit multiplicity versus detection efficiency for chambers operating at different high voltages [40]. Based on these tests we have developed a base design of RPCs for the digital hadron calorimeter. We are confident that these chambers will perform as required for the prototype beam tests. Prototype Section of a Digital Hadron Calorimeter. In order to contain most of the hadronic showers initiated by hadrons of energy 1–50 GeV, we plan to build a prototype hadron calorimeter of 1 1 1× × m3. The section will consist of 40 layers of stainless steel plates with a total layer thickness of 20 mm interleaved with either GEMs or RPCs as the active detector. Each active layer will contain 104 readout pads with an area of 1 cm 1 cm× . The mechanical structure [41], including the absorber plates and a movable table for the test beam, is being designed and assembled at DESY, Germany. The structure will be used for the analog hadron calorimeter being developed by the CALICE collaboration [42], as well as by the two types of digital hadron calorimeter prototypes presented in this proposal. Test Beam Program and Timeline. The prototype modules described in this proposal form a major part of a coherent beam test program [1] to develop high performance calorimeter systems for future International Linear Collider detectors. Two of the participating institutions (UTA and ANL) are members of the international CALICE collaboration. In addition to the DHCAL modules described here, CALICE will also be testing an ECAL prototype and a scintillator tile-based analog HCAL prototype. The ECAL in this MRI proposal is a second generation design with finer lateral segmentation and integrated front-end readout. This proposal represents a significant U.S. ILC detector R&D effort needed to remain competitive with similar efforts in Europe and Asia. All prototype modules will be used to collect data in a test beam at Fermilab during the period 2006–2008, as the last phase of this project. The order of testing the modules depends on the details of the development cycle for each device. However, we expect the first of our three prototype modules will be exposed to beam in late 2006/early 2007. The data from all these beam tests will be critical to the design, implementation, operation and simulation of a new generation of collider detectors. Electronic Readout System for Digital Hadron Calorimeters. Considerable effort is dedicated to the development of the electronic readout system, a challenge by itself, given the large number of channels, of order 4 10× 5 for the prototype and 5 10× 7 for an entire DHCAL. This development is the primary focus of the hadronic calorimeter portions of this proposal. The electronics will be suitable for both the GEM and the RPC readout. The gain of the front-end will be adjustable to accommodate the different signal sizes of the two devices.

The electronic readout system consists of several stages: a) the front-end ASIC whose support is requested in this proposal; b) the data concentrator; c) a VME-based data collector; and d) a trigger and timing system. In the following we briefly describe the individual stages:

a) The front-end ASIC receives signals from 64 individual pads. The signals are shaped, amplified, and discriminated. The resulting hit patterns are time stamped and stored at a speed of 10 MHz. In triggered mode, an external trigger selects the events to be passed on to the data concentrator. In triggereless mode any hit pattern with at least one hit will be written out. The ASICs will be located directly on the PC boards containing the readout pads of the chambers. A first version of the ASIC will be submitted for prototyping in early 2005. The engineering design effort is being provided by Fermilab and Argonne National Laboratory.


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b) The data concentrators receive data from 12 individual ASICs. They mainly consist of FPGAs and will be located on the side of the 1 m3 prototype section of the hadronic calorimeter.

c) The data collector is VME–based and receives the output of the data concentrators. Each card will connect to 12 individual data concentrators. The system specifications are very similar to the recently developed system for the MINOS test beam effort.

d) The trigger system distributes the trigger information to the data concentrators. The timing system provides the clocks and clock resets of the readout system.

Given the relatively small and well definable nature of the back-end electronics (items b–d above), the support for these will come from all the contributing institutions listed in Table 2 through other channels of funds, such as the DOE LCRD program. 5. Impact of Infrastructure

We expect that the scientific results of this project will have a significant impact on the design of the ILC detectors [23–25]. Determination of fundamental detector parameters, such as tracker diameter and magnetic field strength, will result from optimizations which include jet resolution as a major input. This project will provide a solid base for understanding the dependence of the jet energy resolution on the parameters of a given detector design. Hence, we expect that the results of this project will be highly visible and widely cited by the ILC community. This community currently includes hundreds of scientists world-wide and is expected to grow significantly over the next several years. Outside the ILC community, PFA concepts will likely play a role in detector optimization efforts for other HEP experiments where the precision for measuring hadronic final states is limited by detector resolution (rather than intrinsic limitations such as QCD processes).

The data collected with the three prototype detectors will be of paramount importance in tuning existing Monte Carlo simulations of hadronic showers. They will constitute a database likely to be used for many years after the completion of the test beam program.

The three proposed prototype calorimeters will test novel calorimeter concepts not previously investigated. These concepts will likely lead to their application by other HEP experiments and disciplines even outside high energy physics.

Our goal is to make the test beam data available to the general community in an accessible form. University groups will find the data useful for student projects, especially institutions such as four-year colleges and smaller universities, which do not otherwise have direct involvement with experiments at HEP facilities. We would strive to illustrate by example how students at other institutions might perform research projects on these datasets. We plan to maintain a web site which highlights these activities and makes the data set available.

It is conceivable that an outside researcher involved in simulation studies will request a dataset for an experimental condition (e.g., beam condition, detector configuration) which has not been considered by the proponents of this project. Since we will operate the prototype modules at a test beam facility for several years, such special data runs are possible. We will be open to such requests, maximally exploiting the instrumentation constructed through the funds requested in this proposal.

UTA and UO already have strong records of student research in ILC-related activities. We have found the ILC-related projects to be especially well suited for undergraduate science majors and Masters’ student thesis projects. UTA has already produced two physics Masters’ theses [15, 43] from GEM DHCAL projects. At UO, about half of the undergraduate researchers in the HEP group over the last five years have been women. Undergraduate theses have resulted from the work of four of these students, three of whom are women. It seems clear that students who get involved in undergraduate research are more likely to pursue a career in scientific research. 6. Intellectual Merit

The Linear Collider is the next generation, large scale, high energy accelerator that enables high energy physicists to perform measurements of fundamental constituents of matter and the forces between them with an unprecedented precision. This facility will further, among others, our understanding of the origin of mass, provide vital input to astrophysics and cosmology, and likely discover new particles as predicted by current extensions of the Standard Model. The precision demanded by the experiments at this new facility


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can only be met with novel technologies. The three technologies to be investigated in this proposal extend the traditional functionalities of calorimeters into a new regime and will help the linear collider community to determine the optimal technologies for the design of ILC detectors. One electromagnetic and two types of digital hadronic calorimeter prototypes will be constructed and tested. The fine granularity of their readout has never before been achieved. Thus the proposed test beam program will exploit the capability of the prototype modules to dramatically deepen our knowledge of hadronic showers. The program will provide the means to develop particle flow algorithms aimed at improving hadronic jet energy resolution for the linear collider detectors and further the capability of detailed simulation of hadronic showers for the future. 7. Broader Impact

The challenges raised by the linear collider physics program promote the development of new detector technologies. The detectors in this proposal need signal processing with front-end electronics embedded into the sampling gaps, yet maintaining a small gap size to keep particle showers from broadening excessively. A silicon-tungsten electromagnetic calorimeter with embedded electronics contained in 1 mm thick sensitive gap has never been constructed. The Gas Electron Multiplier (GEM) detector has never been used or built on the large scale needed to work in a calorimeter. Resistive Plate Chambers (RPC) have never been used in a calorimeter with fine granularity. Finally, a digital hadron calorimeter for a collider detector has never before been constructed.

These technological challenges require close collaboration between detector development groups both in universities and national laboratories. Some of these efforts also require close collaboration with industry to meet the demand in quantity. The research in frontier technology to develop the prototype modules in this proposal will involve graduate and undergraduate students of physics and engineering, providing ample opportunity to participate in advanced research and development activities. UTA’s 26,000 and UO’s 20,000 students are the immediate benefactors of this program.

All three participating institutions are Quarknet [44] educational outreach centers. Thus, the research activities in development and construction of the prototype modules will also provide high school teachers and their students with opportunities in realizing a new generation of calorimeters. These new detector technologies and the associated by-products will open the gate to possible new detection techniques for medical and other usages, including surveillance for national security and non-destructive inspection of cargo. This program will produce numerous physics and engineering graduate degrees through the analysis of the pre-prototype and beam test data, subsequent algorithm development, development of new electronics and other associated technologies. The results from this program will be disseminated through national and international conferences and workshops and published in peer-reviewed journals. 8. Conclusions

The three calorimeter prototype modules and their corresponding front-end readout electronics to be developed and built through the support from this proposal employ new technologies that have never been used in large scale collider experiments. The performance of these devices will be measured in the beam test program [1] planned at Fermi National Accelerator Laboratory. The International Linear Collider community can use the results of these tests to fine tune detector designs. The data collected from the beam tests will be analyzed to advance the understanding of the behavior of hadronic showers for the linear collider detector and algorithm development. The data will be archived for future use in the simulation of particle detectors. The novel technologies investigated through this proposal will provide a basis for further use in commercial applications, such as in health care and national security. 9. Management Plans Project Director: The principal investigator of this proposal, Professor Jaehoon Yu of the Physics Department at the University of Texas at Arlington, will serve as the project director. The director will have primary responsibility for overseeing the mission of the project. This includes providing oversight of budgetary matters and communication with the funding agency. He will chair the Executive Committee and may take on other specific responsibilities for day-to-day operations. He will prepare annual reports for the Executive Committee and for the project. Executive Committee: The project will be managed by the executive committee, chaired by the project director, and consisting of one representative from each institution. Each committee member will have one


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vote regarding collaboration matters. The chair will only facilitate the vote unless a tie-breaking vote is necessary. The board will organize collaboration meetings and workshops. The board is responsible for arranging the annual project review by an internal panel and for receiving and reviewing annual reports. The executive committee is responsible for determining conference participation and publication activities on behalf of the collaboration. It is also responsible for establishing and implementing education and outreach activities. The board has the responsibility to inform the collaboration of project progress and review results. Technical Board (TB): The collaboration will identify one technical representative on six areas of the project: Si-W ECAL development, ECAL front-end electronics, GEM DHCAL development, RPC DHCAL development, DHCAL front-end electronics and DAQ. The TB will also include representatives from other critical tasks for the overall test beam program. The TB coordinates the overall integration of the various tasks to accomplish the two ultimate goals of this proposal. The TB is also responsible for planning and monitoring progress of various tasks. The board will set milestones for technical aspects of the project. Technical personnel and other collaboration members will participate in bi-weekly video conferencing to review progress and to exchange information about technical issues. TB will also meet at each collaboration meeting and report to the executive board on progress and plans for the future. Collaboration Meetings and Workshops: The collaboration will hold semi-annual meetings in conjunction with workshops at member institutions. The workshops will be open to other ILC detector R&D efforts in order to facilitate the dissemination of results from this project. We will exploit world-wide ILC workshops and conferences as much as we can for dissemination of results. Internal Review: The project will be internally reviewed at the end of each project year as part of a collaboration meeting and workshop. The EC will form an internal review panel. This review panel will evaluate progress of the project in both technical aspects and management and make recommendations to aid in the efficient completion of the project goals. Results from the review will be reported to the technical board and the collaboration by the executive board chair at the collaboration meeting. The TB is required to present plans to implement review board recommendations within two months of the review to the EC. Project Self-evaluation Plan: The tasks milestone goals specified in Table 3 will be reviewed at each semi-annual collaboration meeting. The total number of tasks accomplished will be used as the measure of success for each project year. Each task will generate documentation to keep a record of all activities within the collaboration. The total number of such documents will also measure the success of the project. International Collaboration: Given the fact that all collaborators on in the project are actively engaged in ILC detector R&D efforts and some are members of an international calorimeter R&D collaboration, CALICE, the results from this project will naturally be shared with colleagues from many countries. We plan to participate in international meetings and workshops, to exchange information with colleagues from other countries, and to keep up with and contribute to other detector R&D efforts. Project Management: Various computing applications, such as Microsoft Project, will be used to aid inter-relationship between different projects and their impact to the overall schedule of the project. 10. Responsibilities of participants University of Texas at Arlington. Dr. Yu will act as the project director. He will also be responsible for simulation and software efforts for GEM based DHCAL. Dr. White will be responsible for development and construction of GEM–based DHCAL. Drs. Brandt and De will assist Drs. Yu and White in the GEM DHCAL development effort. They will help supervising students. Argonne National Labortory. Dr. Repond is the Co-PI who will be responsible for overall development and construction of RPC–based DHCAL as well as DHCAL electronics. Dr. Underwood will be responsible for RPC detector and electronics development. Dr. Xia will be responsible for detector testing and software development for RPC–based DHCAL. Mr. Drake, the head electronics engineer, and Dr. Wicklund will be responsible for the design and development of DHCAL electronics. University of Oregon. Dr. Frey is the Co-PI who will be responsible for overall development and construction of Si–W based ECAL as well as ECAL electronics development. Dr. Strom will be responsible for the integrated Si detector development. Dr. Brau will assist Drs. Frey and Strom in Si-W ECAL development effort. He will help supervising students.


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11. Work Breakdown Structure and Task Division Table

The tables presented in this section list work breakdown structure and task assignments.

Tasks timeline

Primary Sub Subsub Expt. cost

$K Start Duration (mo)

deliverables parts Responsible

1.1.1 Specifications PH, EE na Sep-03 5 Document Drake, PH 1.1.2 Design EE na Jul-04 9 Design FNAL 1.1.3 Prototyping EE na Mar-05 3 Chips Drake, PH 1.1.4 Tests EE,PH na Jun-05 2 PC boards Drake, PH 1.1.4 Design-iteration EE na Aug-05 2 Design FNAL

1.1.0 Front-end

ASICs

1.1.5 Production ET 400 Oct-05 4 Chips Repond, Drake1.2.1 Specifications EE,PH na Sep-04 6 Document Drake, PH 1.2.2 Design EE na Jun-05 2 Design FNAL 1.2.3 Prototyping ET na Aug-05 2 Stuffed Bd. ICs FNAL 1.2.4 Standalone tests EE,PH na Oct-05 1 Document EE,PH 1.2.5 Tests with ASIC PH, EE na Oct-05 2 Document EE,PH 1.2.6 Design iteration EE na Dec-05 1 Design Drake

1.2.0 Front-end readout boards

1.2.7 Production ET 100 Jan-06 3 Stuffed Bd. ICs Repond, Drake1.3.1 Specifications EE,PH na Sep-04 6 Document Drake, PH 1.3.2 Design EE na Mar-05 3 Design Chicago 1.3.3 Prototyping EE na Jun-05 3 Board ICs Chicago 1.3.4Tests EE,PH na Sep-05 2 Document Chicago 1.3.5 Design iteration EE,PH na Nov-05 2 Design Chicago

1.3.0 Concentrator

1.3.6 Production ET na Jan-06 3 Stuffed Bd. ICs Chicago 1.4.1 Specifications PH, EE na Sep-04 6 Document Drake, PH 1.4.2 Design EE na Mar-05 3 Design Boston 1.4.3 Prototyping EE na Jun-05 3 Stuffed Bd, Boston 1.4.4 Tests PH, EE na Sep-05 2 Document Boston 1.4.5 Design iteration EE,PH na Nov-05 2 Design Boston

1.4.0 Data

Collector

1.4.6 Production EE,PH na Jan-06 3 Stuffed Bd. ICs Boston 1.5.1 Specifications EE, PH na Sep-04 6 Document Drake, PH 1.5.2 Design EE na Mar-05 3 Design EE, White 1.5.3 Prototyping EE na Jun-05 3 Stuffed Pb. EE 1.5.4 Tests EE, PH na Sep-05 2 Document EE,White 1.5.5 Design iteration EE,PH na Nov-05 2 Design EE, White

1.5.0 Timing and

trigger system

1.5.6 Production EE na Jan-05 3 Stuffed Bd. EE 1.6.1 Specifications EE na Jan-05 6 Document Iowa 1.6.2 Tests ET na Jun-05 1 Document Iowa 1.6.0 Power

Supplies 1.6.3 Acquisition ET na Jan-05 3 P. supplies Iowa 1.7.1 Tests with RPCs PH na Sep-05 9 Document PH

1.0.0 Gas Cal.

DAQ

1.7.0 Int. Test 1.7.2 Tests with GEMs PH na Sep-05 9 Document PH 2.1.1 Design ME na Jan-05 2 Design ME, PH 2.1.2 Prototyping ME, MT na Mar-05 1 Chambers ME, MT, PH 2.1.0 RPC 2.1.3 Production ME, MT 20 Jul-05 12 Chambers ME, MT, PH 2.2.1 Design ME na Jan-05 2 Design Iowa

2.0.0 DHCAL

with RPCs 2.2.0 Gas

system 2.2.2 Production ME, MT na Jul-05 3 Gas system Iowa 3.1.1 Design PH na Dec-04 3 Design foils White 3.1.2 Artwork 3M 20 Apr-05 3 Masks White 3.1.3 Production 3M 150 Nov 05 4 foils foils White, Yu

3.1.0 GEM foils

3.1.4 Testing PH na Dec 05 2 foils cert-foils Li 3.4.1 Acq. Strong-backs GA 5 Oct 05 1 Strng backs Steel White, Li 3.4.2 Fab foil stretch-jig PH na Jun 05 2 Jig Al struts Li 3.4.3 Design walls PH na Feb 05 2 Walls Foam/tape Li/White

3.4.4 Design spacers PH na Feb 05 2 Spacers Li/White

3.0.0 DHCAL

with GEMs 3.4.0 Active

layer components

3.4.5 Gas in/outlets PH na Mar 05 1 Pipes tubing White


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Tasks timeline

Primary Sub Subsub Expertise cost

$K Start Duration (Mo)

deliverables parts responsible

3.5.1 Design PH na Apr 05 2 Document Li 3.5.2 Assemble GA 5 Oct 05 3 Gas supply Mf., vlv White3.5.0 Gas system 3.5.3 Install PH,GA na Mar 06 2 Li

3.6.0 GEM lyr. 3.6.0 UTA na Jan 06 8 GEM chmbrs Li

3.0.0 GEM

DHCAL 3.7.0 Test GEM 3.6.0 PH na Feb 06 8 CertGEM lyrs Chamb. White

4.1.1 specify PH na Done Document Frey 4.1.2 procurement PH na Done W plates Frey 4.1.0 Tungsten 4.1.3 QC GA na Jun-05 1 QC Certification Frey 4.2.1 bump-bond trials – existing prototypes PH,ET na Aug-05 2 Functional

prototypes Proto.+ ASICs Frey

4.2.2 signal tests – existing prototypes PH,GA na Oct-05 2 document, paper Proto. +

ASICs Frey

4.2.3 noise sim. PH na Dec-05 2 document Strom4.2.4 metal. layout PH,ET na Jan-06 2 document Frey 4.2.5 Purchase PH 70 Mar-06 6 NRE, photomasks Frey 4.2.6 delivery 100 Sep-06 bare Si dets Frey 4.2.7 lab Si QC PH, GA na Sep-06 5 QC Certification dets Strom4.2.8 signal tests PH, GA na Oct-06 5 document dets Strom4.2.9 bump-bonding ET, PH na Dec-06 3 Complete Si dets dets Frey 4.2.10 interconnects ET na Feb-07 1 det assembly above Strom

4.2.0 Silicon detectors

4.2.11 full lab tests PH, GA na Mar-07 2 detectors above Strom4.3.1 m-board design PH, EE na Jan-06 2 document SLAC

4.3.2 mbd procure PH na Mar-06 2 50 boards Strom4.3.3 bias conn. Des. PH, EE na Nov-05 2 document Strom4.3.4 lumped comp. PH, EE na Jan-06 1 document SLAC4.3.5 ground connect PH, EE na Nov-05 1 document all 4.3.6 heat path sim. PH, ME na Dec-05 3 document SLAC

4.3.0 Electro-mechanical

4.3.7 thermal design ME na Mar-06 3 document SLAC4.4.1 design ME, PH na Mar-06 6 document SLAC4.4.2 mockup PH, GA na Jul-06 3 mechanical proto. Strom

4.0.0 Ecal Si-

W

4.4.0 module mechanics

4.4.3 assembly ME, PH na Nov-06 5 Comp. module All All 5.1.1 analog design EE na Nov-05 5 document Proto. SLAC5.1.2 digital design EE na Nov-05 5 document Proto. SLAC5.1.3 prep. 0.25 µm EE na Apr-06 1 Fab. ready above SLAC5.1.4 Purchase PH, EE 70 May-06 2 photomasks, NRE Frey

5.1.0 ASIC

5.1.5 delivery, test EE na Aug-06 2 ASICs ready SLAC5.2.1 design EE na Mar-06 1 document SLAC5.2.0 data

concentrator+B3 5.2.2 test EE na Jun-06 1 10 chips SLAC5.3.1 design PH na Mar-06 3 document Strom5.3.2 acquire modules EE, PH na Jun-06 6 all

5.0.0 A3 Ecal electroni

cs

5.3.0 data acquisition

5.3.3 test beam setup PH, GA na Mar-07 2 can acquire data all Legends: PH: Physicist, EE: Electrical Engineer, ET: Electrical Technician, GA: Student assistant, 3M: 3M Cooperation, dets: Si detectors, proto.: prototype, ME: mechanical engineer, MT: Mechanical Technician, Li: Dr. Jia Li from UTA, Mfl.: Manifolds, vlv: Valve, Chamb.: Chambers Costs: Costs are in $1000 units. na: Not applicable since the support for the task is not requested in this proposal.

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