120475830
Physics capabilities of the DO upgrade detector
The D0 detector at Fermilab is being upgraded to meet the demands imposed by high luminosity Tevatron running planned to begin in 1998. The central tracking detectors will be replaced with silicon and scintillating fiber tracking systems inside a solenoidal magnetic field and a preshower detector will be added to aid in electron identification. The design and performance of these systems are described and detailed simulations of the physics capabilities of the upgraded detector are presented. In particular the authors focus on the study of electroweak boson properties and top quark physics and briefly describe the b-physics capabilities.
110084127
A silicon drift photodiode
A low-capacitance photodiode based on the principle of the solid-state drift chamber has been constructed and tested. The device is based on a cellular design with an anode at the center of each of five cells, allowing electrons liberated by ionization to drift up to 1 mm to the readout strip. Two designs were produced with p/sup +/ implant widths of 75 mu m and 85 mu m, respectively, using n-type material of 3.5-k Omega -cm resistivity. The opposite surface is a uniform p-type implant, features matching those of the other surface, and is unmetallized to ensure good photosensitivity. Results on the performance of the detector, including leakage current, capacitance, and drift properties, are presented and compared with simulation results. >
122654690
Silicon microstrip wedge detectors for the DØ silicon tracker
Abstract The silicon tracking system proposed for the DO upgrade is discussed. The design of “wedge” modules for the forward disk section of the tracker is described. The wedge detectors are double-sided with a stereo angle of ± 15° and a strip pitch of 50 μm. Each strip includes an integrated ac-coupling capacitor and polysilicon bias resistor. First results from recently fabricated prototype wedge detectors are presented.
122003047
Silicon drift photodiodes
Abstract Low capacitance photodiodes based on the principle of the solid state drift chamber have been constructred and tested. The devices are based on a cellular design with an anode at the centre of each of five cells allowing electrons liberated by ionisation to drift up to 1 mm to the readout strip. Results on the performance of the detectors, including leakage current, capacitance and drift properties, are presented and compared with simulations. A second series drift photodiodes have been processed which incorporate improvements based on results acquired from the first design. They have leakage currents of a few nA and shorter drift times at the periphery of the drift cells. We present measurements showing the performance of the new devices.
110541630
Punch-through currents and floating strip potentials in silicon detectors
Punch-through currents flowing between adjacent p/sup +/ strips on the surface of silicon microstrip drift detectors have been observed. Measurements of the floating strip potential have shown that a p/sup +/ strip acquires a voltage such that the punch-through current and the leakage current are equal and opposite. The factors influencing the threshold for the punch-through effect have been compared with a simple computer model, and the predicted variation with the interstrip gap is found to be in reasonable agreement with measured values for a variety of detectors. >
110503904
Silicon detector tests with the RAL microplex readout chip
The design, construction and operation of a five-layer silicon microstrip detector is described. The detector consisted of silicon microstrip wafers bonded to the RAL Microplex MX2 readout chip. The readout chip provided amplification with double-correlated sampling for each microstrip channel and multiplexing of 128 signals. The circuitry controlling the chip, the readout electronics, the stage holding the microstrip wafers and their alignment, are also described. A single-layer resolution of 10±0.6 μm was obtained in a test beam. This work is part of a program to design a microvertex detector for UA1 at the CERN pp collider.
17542978
CSR EFFECTS IN A BUNCH COMPRESSOR: INFLUENCE OF THE TRANSVERSE FORCE AND SHIELDING ∗
We studytheinsuenceofcoherentsynchrotronradiation(CSR) on particle bunches traveling on arbitrary planar or-bits betweenparallelconductingplates whichrepresentthevacuum chamber. Our ultimate goal is to follow the timeevolution of the phase space density distribution by solv-ing the 2D Vlasov-Maxwell (VM) system in the time do-main. In contrast to macroparticle methods, the VM ap-proach has no statistical noise and is better suited to thestudy of microbunching. The Þelds excited by the bunchare computed in the lab frame, while the nonlinear Vlasovequation, formulated in interaction picture, is integrated inthe beam frame using the method of local characteristics(Perron-Frobenius (PF) method). The interaction pictureallows a relatively large step using the Euler method. De-tails of our method can be found in [1] and [2]. The majordifÞculty here is the need for a detailed understanding ofthe support of the phase space density. Here we show re-cent numerical results obtained in our Liouville-Maxwellapproximation (LMA) for the benchmark bunch compres-sor at 5 GeV studied in [3]. We analyze the role played bythe transverse force and the effect of shielding and studythe supportof the phase space density.
123033636
The influence of anharmonic potentials in calculations of planar channeling radiation from GeV positrons
Abstract The frequency of radiation from planar channeled positrons in the GeV region is discussed for realistic planar potentials when the dipolarity condition is not satisfied. It is found that there is a critical beam momentum at which the maximum radiated frequency is practically the same for all channeled positrons. For this momentum a sharp peak in the calculated composite spectrum is to be expected and this could explain the sharp peaking observed in a recent CERn experiment for 5 GeV/ c positrons.
42499879
Simulation of Bunch Lengthening and Sawtooth Mode in the SLAC Damping Rings
The authors study longitudinal coherent motion of a stored electron beam by a time domain integration of the nonlinear Vlasov-Fokker-Planck equation. For the present SLAC damping rings the authors found several features in agreement with experiment. This report emphasizes the earlier vacuum chamber of the rings, replaced in 1992--93. Nonlinear effects are much stronger for the old chamber, and the computed phenomena more various.
10238716
From symplectic integrator to poincaré map: spline expansion of a map generator in Cartesian coordinates
Abstract Data from orbits of a symplectic integration can be interpolated so as to construct an approximation to the generating function of a Poincare map. The time required to compute an orbit of the symplectic map induced by the generator can be much less than the time to follow the same orbit by symplectic integration. The approximation has been constructed previously for full-turn maps of large particle accelerators, and a large saving in time (for instance a factor of 60) has been demonstrated. A shortcoming of our work to date arises from the use of canonical polar coordinates, which preclude map construction in small regions of phase space near coordinate singularities. Here, we show that Cartesian coordinates can be used, thus avoiding singularities. The generator is represented in a basis of tensor product B-splines. Under weak conditions, the spline expansion converges uniformly as the mesh is refined, approaching the generator of the Poincare map as defined by the symplectic integrator, in some parallelepiped of phase space centered at the origin.
55374019
Effect of betatron motion on the septum flux in superslow extraction at the SSC
A scheme for the superslow extraction of protons from the SSC rings for high energy test beam or precision fixed-target B physics is currently being investigated. The flux onto the extraction septum (a curved Si crystal) is to be generated by diffusion produced by noise injected into the RF system. The extraction rate depends on both the diffusion of the closed orbit (due to dispersion at the crystal) and the horizontal betatron amplitude of the diffusing protons. The diffusion of the closed orbit has previously been described by the one-dimension longitudinal diffusion theory of Dome (1984) and Krinsky and Wang (1982). In this paper, we extend this theory to include the effect of the betatron motion. Comparisons with Monte Carlo tracking simulations are made.<<ETX>>