ALICE electromagnetic calorimeter prototype test

This Memorandum of Understanding between the Test Beam collaborators and Fermilab is for the use of beam time at Fermilab during the Fall, 2005 Meson Test Beam Run. The experimenters plan to measure the energy, position, and time resolution of prototype modules of a large electromagnetic calorimeter proposed to be installed in the ALICE experiment at the LHC. The ALICE experiment is one of the three large approved LHC experiments, with ALICE placing special emphasis on the LHC heavy-ion program. The large electromagnetic calorimeter (EMCal) is a US initiative that is endorsed by the ALICE collaboration and is currently in the early stages of review by the Nuclear Physics Division of the DOE. The installation in the test beam at FNAL and test beam measurements will be carried out by the US members of the ALICE collaboration (ALICE-USA). The overall design of the ALICE EMCal is heavily influenced by its location within the ALICE L3 magnet. The EMCal is to be located inside the large room temperature magnet within a cylindrical integration volume approximately l12cm deep, by 5.6m in length, sandwiched between the ALICE TPC space frame and the L3 magnet coils. The chosen technology is a layered Pb-scintillator sampling calorimeter with a longitudinal pitch of 1.6mm Pb and 1.6mm scintillator. The full detector spans {eta} = -0.7 to {eta} = 0.7 with an azimuthal acceptance of {Delta}{phi} = 120{sup o}. The EMCal readout is of a ''Shish-Kabob'' type similar to the PHENIX Pb-scintillator sampling calorimeter in which the scintillation light is collected via wavelength shifting fibers running through the Pb-scintillator tiles perpendicular to the front surface. The detector is segmented into {approx}14000 towers. The basic structural units of the calorimeter are supermodules, each subtending approximately {approx}20{sup o} in {Delta}{phi} and 0.7 units in {Delta}{eta}. Supermodules are assembled from individual modules. The modules are further segmented into 2 x 2 individually read out towers. The fibers from an individual tower are grouped together to form readout tower bundles. These are each optically coupled to an avalanche photodiode (APO) via a short light guide to provide some spatial optical mixing and to match the fiber bundle to the APO. The module assembly is indicated in Figure l. The supermodules weigh about 9.6 tons and are the basic units handled during installation. Each supermodule is roughly I45cm wide at the front surface by 350cm long with an active depth of 24.5cm (at {eta} = 0) plus an additional 6.6 cm of depth in structural plates. The physical characteristics of the ALICE EMCal are summarized in Table 1. The EMCal test beam measurements at FNAL will utilize a stacked 4 x 4 array of prototype EMCal modules (8 x 8 towers). All towers will be instrumented with the same model APO and preamplifier as will be used in the ALICE experiment and all channels will be readout with existing prototype front end electronics intended for use in ALICE. The goals of the test beam measurements are: To investigate the energy resolution, linearity, uniformity, and position resolution, using electron beams; To study the energy dependence of the response to electrons and hadrons to determine the particle identification capabilities of the EMCal by shower shape; And to investigate the timing characteristics of the energy signal for crude time-of-flight measurement ({approx} 1ns) for use for anti-neutron rejection. Measurements will be made for comparison with different signal shaping times in the front end electronics

Point-to-point readout for the ALICE EMCal detector

AbstractIt is anticipated that the LHC will deliver Pb+Pb collisions at a minimum bias interaction rate of about 50kHz after the second long shutdown of the LHC in 2018. This will be roughly two orders of magnitude greater than the current data recording rate capability of the ALICE experiment. Therefore a major upgrade of the ALICE detector is planned for the next shutdown to enable ALICE to record data at the full Pb+Pb minimum bias interaction rate delivered by the LHC. A new point-to-point readout system for the electromagnetic calorimeter (EMCal) of ALICE has been developed, to replace the legacy readout bus, that essentially accomplishes this goal, and is being installed during the current LHC shutdown (2013–2014). The new readout uses the existing EMCal front end electronics yet provides more than an order of magnitude decrease in the readout time, to about 21μs, with modest cost and effort

Highlights from PHENIX - II

This contribution highlights recent results from the PHENIX Collaboration at RHIC with emphasis on those obtained through lepton and photon measurements in PHENIX.Comment: 9 pages, 13 figures, presented at the 20th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions - "Quark Matter 2008", Jaipur, India, February 4-10, 200

Front-end electronics for the ALICE calorimeters

The ALICE calorimeters PHOS and EMCal are based on Avalanche Photo-Diode (APD) photosensors with Charge Sensitive Preamplifiers (CSP) for readout of the scintillating elements. The amplified signals are read out via 32-channel shaper/digitizer front-end electronics (FEE) with 14-bit effective dynamic range. The electronics is based on second order shapers with dual gain for each channel, getting digitized by ALTRO chips. Each APD channel is equipped with an individual 10-bit APD gain adjustment and 2×2 channel clusters generate a 100 ns shaped analog sums output (Fast OR) for the associated Trigger Region Units (TRU). The Fast OR signals are generated by first order shapers with a dynamic range of 12-bit given by the ADC in the TRU cards. Board controller firmware in the FPGA provides local monitoring and configuration of all parameters via the ALICE DCS system. The signal to noise ratio for MIP at 215 MeV is not, vert, similar7 per channel with a noise level of 30 MeV at room temperature for a dynamic range of 80 GeV for PHOS, and the fast-OR RMS noise level is about 75 MeV for a dynamic range of 250 GeV for EMCal

Hierarchical trigger of the ALICE calorimeters

The trigger of the ALICE electromagnetic calorimeters is implemented in 2 hierarchically connected layers of electronics. In the lower layer, level-0 algorithms search shower energy above threshold in locally confined Trigger Region Units (TRU). The top layer is implemented as a single, global trigger unit that receives the trigger data from all TRUs as input to the level-1 algorithm. This architecture was first developed for the PHOS high pT photon trigger before it was adopted by EMCal also for the jet trigger. TRU units digitize up to 112 analogue input signals from the Front End Electronics (FEE) and concentrate their digital stream in a single FPGA. A charge and time summing algorithm is combined with a peakfinder that suppresses spurious noise and is precise to single LHC bunches. With a peak-to-peak noise level of 150 MeV the linear dynamic range above threshold spans from MIP energies at 215 up to 50 GeV. Local level-0 decisions take less than 600 ns after LHC collisions, upon which all TRUs transfer their level-0 trigger data to the upstream global trigger module which searches within the remaining level-1 latency for high pT gamma showers (PHOS) and/or for Jet cone areas (EMCaL)

Hadron calorimetry test bench

A reconfigurable sampling hadron calorimetry test bench was built. Different scintillator-absorber stack configurations can be easily constructed within the test bench for extensive detector performance studies. Three configurations, with absorber layers of uniform thicknesses of 48 mm, 24 mm, and 16 mm, and with scintillator layers of uniform thicknesses of 4 mm, were studied with electron and hadron beams