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The Large Hadron Collider (LHC), presently under construction at CERN, requires monitoring the parasitic charge in the 3.3 ms long gap in the machine fill structure. This gap, referred to as the abort gap, corresponds to the raise time of the abort kickers magnets. Any circulating particle present in the abort gap at the time of the kickers firing is lost inside the ring, rather than in the beam dump, and can potentially damage a number of the LHC components. CERN specifications indicate a linear density of 6 x 106 protons over a 100 ns interval as the maximum charge safely allowed to accumulate in the abort gap at 7 TeV. We present a study of an abort gap monitor, based on a photomultiplier tube with a gated microchannel plate, which would allow for detecting such low charge densities by monitoring the synchrotron radiation emitted in the dedicated diagnostics port. We show results of beam test experiments at the Advanced Light Source (ALS) using a Hamamatsu 5961U MCP-PMT, which indicate that such an instrument has the required sensitivity to meet LHC specifications.

We report on the development of an instrument for the measurement of the longitudinal beam profile in the Large Hadron Collider (LHC). The technique used, which has been successfully demonstrated at the Advanced Light Source, mixes the synchrotron radiation with the light from a mode-locked solid state laser oscillator in a non-linear crystal. The up-converted radiation is then detected with a photomultiplier and processed to extract, store and display the required information. A 40 MHz laser, phase-locked to the ring radio frequency system, with a 50 ps pulse length, would be suitable for measuring the dynamics of the core of each of the LHC 2808 bunches in a time span much shorter than the synchrotron period. The same instrument could also monitor the evolution of the bunch tails, the presence of untrapped particles and their diffusion into nominally empty RF buckets ("ghost bunches") as required by the CERN specifications.

We report on the development of a new technique for the measurement of the longitudinal beam profile in storage rings. This technique, which has been successfully demonstrated at the Advanced Light Source, mixes the synchrotron radiation with the light from a mode-locked solid state laser oscillator in a non-linear crystal. The up-converted radiation is then detected with a photomultiplier and processed to extract, store, and display the required information. The available choices of laser repetition frequency, pulse width, and phase modulation give a wide range of options for matching the bunch configuration of a particular storage ring. Besides the dynamic measurement of the longitudinal profile of each bunch, the instrument can monitor the evolution of the bunch tails, the presence of untrapped particles and their diffusion into nominally empty RF buckets ("ghost bunches").

We report on development of a new storage ring operations tool for measurement of longitudinal beam density profile. The technique mixes synchrotron light with light from a mode locked solid-state laser oscillator in a non-linear crystal and detects the up-converted radiation with a photo-multiplier. The laser is phase locked to the storage ring RF system. The laser choices available for repetition frequency, pulse length and phase modulation give a very wide range of options for matching the bunch configuration of particular storage rings. Progress in the technology of solid-state lasers ensures this system can be made robust for routine use in storage ring operations. A very large number of important applications are possible including measurement of the fraction of untrapped particles prior to acceleration, the population of particles in the nominally unfilled RF buckets in a bunch train ("ghost bunches"), longitudinal tails, the diffusion of particles into the beam abort gap and the normal bunch parameters of longitudinal shape and intensity. We are currently investigating application to two devices: (1) the 1.9 GeV ALS electron storage ring at LBNL with 328 RF buckets, 2ns bucket spacing, 276 nominally filled bunches, 15-30ps rms bunch length and (2) the 7 TeV LHC proton collider under construction at CERN with 35,640 RF buckets, 2.5 ns bucket spacing, 2,808 nominally filled bunches, 280-620 ps rms bunch length. A proof of principle experiment is being conducted on ALS. The results of the ALS experiment and detailed analyses of the application to LHC and its requirements are described.

A novel segmented multigap pressurized gas ionization chamber is being developed for optimization of the luminosity of the Large Hadron Collider (LHC). The ionization chambers are to be installed in the front quadrupole and 0[degrees] neutral particle absorbers in the high luminosity interaction regions (IRs) and sample the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The ionization chambers are instrumented with low noise, fast pulse-shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. In this paper, we report the initial results of our second test of this instrumentation in a super proton synchrotron (SPS) external proton beam. Single 300 GeV protons are used to simulate the hadronic/electromagnetic showers produced by the forward collision products from the interaction regions of the LHC. The capability of instrumentation to measure the luminosity of individual bunches in a 40 MHz bunch train is demonstrated. Index Terms--Gas monitor, ionization detector, luminosity monitor, shower detector.

A high-throughput Pulse Height Analyzer system for synchrotron-based applications requiring high resolution, high processing speed, and low dead-time has been developed. The system is composed of a 120 ns 12-bit nuclear quality analog-to-digital converter with a self-adaptive fast peak detector stretcher and a custom-made fast histogramming memory module that records and processes the digitized data. The histogramming module is packaged in a VME/VXI compatible interface. Data is transferred through a fast optical link from the memory interface to a computer. A dedicated data acquisition program matches the hardware characteristics of the histogramming memory module. The data acquisition system allows for different data collection modes. The system can acquire data in synchronization with an external trigger or operate as a standard pulse-height analyzer. Acquisition can be performed on several channels simultaneously. A two-channel prototype has been demonstrated at the Stanford Synchrotron Radiation Laboratory accelerator in conjunction with a fluorescence X-ray Absorption Fine Structure Spectroscopy experiment. A detailed description of the entire system is given and experimental data shown. Index Terms--Accelerator instrumentation, dead-time, high resolution, high speed, pulse height analysis.

The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high-luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (~235 W at design luminosity of [10.sup.34] [cm.sup.-2] [s.sup.-1]). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multigap, pressurized gas ionization chamber is being developed for sampling the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The system design choices have been strongly influenced by optimization of signal-to-noise ratio and by the very high radiation environment. The ionization chambers are instrumented with low-noise, fast, pulse-shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. Data on each bunch are to be separately accumulated over multiple bunch crossings until the desired statistical accuracy is obtained. At design luminosity, approximately 2 x [10.sup.3] bunch crossings will suffice for a 1% luminosity measurement. In this paper, we report the first experimental results of the ionization chamber and analog electronics. Single 450-GEV protons from the SPS at CERN are used to simulate the hadronic/electromagnetic showers produced by the forward collision products from the interaction regions of the LHC. Index Terms--Ionization chamber, luminosity monitor, shower detector.

We constructed two small-area pixelated detectors, which can record signals produced by 800-MeV proton beam micropulses with a repetition rate of 358 ns. The first detector was built around a two-dimensional (2-D) photodiode array. The array was illuminated by light emitted by a monolithic 1.7-mm-thick lutetium oxy-orthosilicate (LSO) scintillator and imaged by a simple optical system. The other detector was a hydrogen ion chamber operated at 1 to 2.5 atm. The anode was divided into an array of 8 x 8 1 [mm.sup.2] pixels. The fast positive-ion drift velocity in hydrogen helps to minimize the space charge build up. However, for beam pulses spaced in time closer than 1 [micro]s, there appears to be a substantial accumulation of space charge. The electronic readout chain, for each of the 64 channels, consisted of an externally clocked fast-gated integrator and an amplifier coupled to an on-board analog-to-digital converter (ADC) and a first-in-first-out storage (FIFO). The detectors were tested with beam pulses up to 4 x [10.sup.6] protons per [mm.sup.2] delivered in 30 to 120 ns wide microbursts. Index Terms--Dynamic radiography, hydrogen gas-ion chamber, lutetium oxy-orthosilicate (LSO) scintillator, photodiode array, proton radiography detectors.