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Shock waves in P-bar target

Description: The deposition of large amount of beam energy in short time will cause high temperature and pressure in the center of P-bar Target, and this disturbance will propagate outwards as a shock wave. Shock wave induced material changes which are of our concern include void growth and accompanying density decrease which will decrease antiproton yield, and crack formation and fracture as was observed in tungsten target which will destroy the integrity of the target. Our objective is to analyze the shock wave behavior in the target, optimize its design so that the destructive effects of shock wave can be minimized, the integrity of the target can be maintained, and a reasonably high yield of antiproton production can be achieved. In this report we put together some results of our analysis of a cylindrical copper target. We hope that it will provide a general overview of the shock wave phenomena in the target, establish a basis for further research, and facilitate the target design. First, energy deposition data are analyzed, and it is justified that as an approximation, the problem can be treated as axi-symmetric. The average data therefore are used as energy profile, however, the maximum energy deposition are still used as the peak value. Next some basic estimations are made as to what temperature and pressure can reach at present level of energy deposition. Then some characteristics of wave propagation in a thermal shock loaded solid are illustrated with a one-dimensional model. Since there is no analytical solution available for cylindrical geometry, our understanding of the problem relies on numerical model, which are performed via finite element package ANSYS. results of numerical analysis are summarized, sources of potential danger are identified, and design ideas to minimize the damage are proposed.
Date: November 1, 1991
Creator: Tang, Zhijing & Anderson, K.
Partner: UNT Libraries Government Documents Department

Antiproton accumulator in the Main Injector era

Description: I propose a new lattice for Fermilab Antiproton Accumulator. The lattice is designed with the aim of implementing higher bandwidth stochastic cooling systems, thus enabling the Accumulator to handle antiproton beam intensities expected in the Main Injector era. The design proposed here satisfies very well all the requirements for the new Accumulator concerning the lattice functions, stochastic cooling parameters, and the tunability of the machine.
Date: September 1, 1992
Creator: Visnjic, V.
Partner: UNT Libraries Government Documents Department

Antiproton Accumulator in the Main Injector era (2)

Description: By adding a single quadrupole per sextant in the Antiproton Accumulator it is possible to obtain a lattice well suited for higher bandwidth stochastic cooling systems such as those anticipated for the Main Injector era. The lattice proposed here has excellent properties concerning both the lattice functions and the stochastic cooling parameters.
Date: December 1, 1992
Creator: Visnjic, V.
Partner: UNT Libraries Government Documents Department

Low energy antiproton possibilities at the AGS

Description: The technical feasibility of creating a pure antiproton beam at the AGS has been studied. The scheme involves an antiproton target station and transport back to the Booster synchrotron, which acts as both a purifier and accelerator/decelerator. This proposal would be very attractive to the user community since this operation could run parasitically (transparently) to the AGS operating modes. The energy range of antiprotons can be as low as 2 MeV to as high as 5 GeV. The intensity of the beam is estimated to be 7 {times} 10{sup 7}/sec above 2.5 GeV/c and 4 {times} 10{sup 4}/sec at 200 MeV/c.
Date: January 1, 1990
Creator: Lee, Y.Y.
Partner: UNT Libraries Government Documents Department

Potential kaon and antiproton beams at BNL

Description: The AGS at Brookhaven is the worlds most prolific producer of kaons and low energy antiprotons during operations. With the imminent operation of the AGS Booster which will increase intensities by an anticipated factor of six in the next few years, it will become possible to have purified beams of particles containing strange quarks and anti-quarks with intensities comparable to the pion beams which have so successfully dominated precision hadron spectroscopy in the past. 10 refs., 3 figs.
Date: January 1, 1991
Creator: Lazarus, D.M.
Partner: UNT Libraries Government Documents Department

Schemes for anti pp interactions at ISABELLE

Description: Various schemes for obtaining anti pp interactions are outlined, and the luminosities obtainable for each case calculated. In the simplest realistic case, a luminosity of 1.3 x 10/sup 29/ is obtained with a 13 hour filling time. The addition of special rf systems in both the AGS and ISABELLE give a scheme with luminosity 8 x 10/sup 29/ in 6 hours. The use of stochastic cooling to stack raises the luminosity to as high as 10/sup 31/ but the filling time is then 68 hours. Finally a scheme is considered that uses a special 30 GeV capture ring. With this, a luminosity of 10/sup 31/ could be achieved after 20 hours, or higher if a larger filling time were acceptable. Further gains could be made if a smaller proton spot on the target is used but a simple calculation suggests that even the spot size assumed may explode the target too fast.
Date: September 8, 1977
Creator: Palmer, R.B.
Partner: UNT Libraries Government Documents Department

Fast 4 to 8 GHz Debuncher betatron stochastic cooling for the Tevatron upgrade

Description: The present 2 to 4 Ghz Debuncher betatron stochastic cooling systems are designed to cool 7 x 10/sup 7/ antiprotons with initial transverse emittances of 20..pi.. mm-mrad down to 7..pi.. mm-mrad in 2 seconds. For the Tevatron upgrade, it would be advantageous to cool twice the number of antiprotons from 20..pi.. mm-mrad to 1..pi..d mm-mrad in half the time. We explore the possibility of achieving this goal with 4 to 8 Ghz stochastic cooling systems. Since the transverse beam size is initially more than twice the width of the cooling electrodes, we compare the effectiveness of one, two, and three plate pairs spaced strategically along the transverse beam direction. We also compare constant gap size electrodes with that for gap sizes which track the beam size as the emittance is reduced. We find that the three plate pair variable gap geometry performs the best, closely followed by the two plate pair variable gap geometry. Because of lower production costs we would suggest use of the latter. 8 refs., 7 figs., 37 tabs.
Date: July 1, 1987
Creator: Mtingwa, S.K.
Partner: UNT Libraries Government Documents Department

Some design considerations for pbar target sweeping station

Description: This report summarizes the results of some recent calculations useful to design the beam sweeping station to produce high intensity pbar beam at AP0. With various on-going and planned intensity upgrade at the accelerator including the main injector the primary beam intensity on the pbar target is expected to increase. But some complications would arise from the existing method of pbar production. A study of the heavy metal targets used when the beam intensity was about 1.0 {times} 10{sup 12}, has shown a clear indication of target destruction by the proton beam. Although the heavy metal has very high melting point temperature the thermoelastic property is not suitable for its use as a reliable pbar target. During 1989 collider run, the target material was changed over to copper because of its better thermoelastic properties. The pbar yield measurement did not show much indications of target destruction except for a small decrease in the pbar yield. However, the calculations showed that the target material along the beam might have had enough energy deposition to transform the target material from the solid state to the liquid state during the beam spill time. A further increase of the proton beam intensity might cause melting of the target and drill a hole. These problems stimulated this investigation of suitable target materials and a method to handle the high intensity proton beam. Properties of a number of target materials have been studied in terms of their mechanical strength/resistance to shock-waves i.e. their thermoelastic behaviour.
Date: June 1, 1991
Creator: Bhat, C.M.
Partner: UNT Libraries Government Documents Department

Squid based beam current meter

Description: A SQUID based beam current meter has the capability of measuring the current of a beam with as little as 30 x 155 antiprotons (with a signal to noise ratio of 2). If low noise dc current is used to cancel most of the beam or an up-down counter is used to count auto-resets this sensitivity will be available at any time in the acumulation process. This current meter will therefore be a unique diagnostic tool for optimizing the performance of several Tev I components. Besides requiring liquid helium it seems that its only drawback is not to follow with the above sensitivity a sudden beam change larger than 16 ..mu..A, something that could be done using a second one in a less sensitive configuration.
Date: November 25, 1983
Creator: Kuchnir, M.
Partner: UNT Libraries Government Documents Department

Automatic steering corrections to minimize injection oscillations in the Fermilab Antiproton Source rings

Description: Missteering of particle beam at injection into a circular accelerator produces coherent betatron oscillations. The beam position monitor system in the Antiproton Source at Fermilab can measure the beam position on each turn around the ring during these oscillations. From the amplitude and phase of the oscillations, corrections to the beamline steering are calculated to remove the oscillations. The analysis includes the case where the horizontal and vertical tunes are quite strongly coupled. This technique has proved to be valuable both in operation of the Fermilab Collider and as an analytical tool. 4 refs., 2 figs.
Date: March 1, 1989
Creator: Harding, D.J. & Riddiford, A.W.
Partner: UNT Libraries Government Documents Department

Debunching into a bucket of lower harmonic number

Description: The adiabatic debunching of beam from buckets of higher harmonic number into waiting buckets of lower harmonic number is a critical step in the current scheme of operation for Tev I. The optimum choice of rf system parameters for this ''bunch coalescing'' process is not immediately obvious. In this note two examples are presented along with generalizations based upon them and experience with the Tevatron I design which can simplify the selection of appropriate parameters for different conditions.
Date: December 9, 1987
Creator: MacLachlan, J.A. & Griffin, J.E.
Partner: UNT Libraries Government Documents Department

Fermilab accumulator magnets vacuum chamber heating system

Description: The Fermi National Accelerator Laboratory (Fermilab) is building an Accumulator Ring to store antiprotons for high energy physics proton-antiproton collisions in the Tevatron accelerator. The Accumulator Ring approximately 474 m in circumference, consists of many quadrupole and dipole magnets connected with stainless steel vacuum chambers for beam circulation. The vacuum pressure required is in the low 10/sup -10/ Torr range. To reach this pressure, the vacuum chambers are bake to 300/sup 0/C each time they have been opened to atmospheric pressure. The critical problem is to bake the chambers in the magnets at high temperature without overheating the laminated magnets. Some of the magnets are 5 m long with very restrictive space for the heaters and insulation. An average space of only 7.5 mm around the chambers is available. In this space a heating system has been designed and tested to heat the chamber to 300/sup 0/C and allow a maximum temperature of 65/sup 0/C nest to the magnet components. This was accomplished by using a heating blanket completely covered with a water cooled copper heat sink jacket to protect the magnet from the high temperatures. The design of a final selected heating blanket is discussed. A prototype test results are given with comparison of calculated and measured temperature distribution.
Date: December 1, 1984
Creator: Satti, J.A. & Lee, G.N.
Partner: UNT Libraries Government Documents Department

Intense antiproton source for a 20 TeV collider

Description: The feasibility of production collecting and cooling anti p's at a rate > 3 10/sup 8/s/sup -1/ is demonstrated. This implies a filling time of approx. 12 hours to reach a luminosity of approx. = 10/sup 32/ cm/sup -2/s/sup -1/ in the collider.
Date: April 1, 1983
Creator: Lambertson, G.R. & Leemann, C.W.
Partner: UNT Libraries Government Documents Department

Measurement of frequency response of LBL stochastic cooling arrays for TeV-I storage rings

Description: Lawrence Berkeley Laboratory (LBL) has developed electrodes for the stochastic cooling system which is used in the anti-proton source in TeV-I at Fermilab. The electrodes are in the form of a pair of stripline couplers or loops, the elements of which are mounted on opposite sides of the beam. We have made two different couplers of similar design, the one to operate in the frequency range 1-2 GHz, the other, 2-4 GHz. We have made two different types of measurements; the one involving the response of a single loop pair to a wire signal simulating the beam signal; the other, the response of a 16 loop-pair array to an actual beam. Both sets of measurements were made in the frequency domain, and both involved taking both the so-called sum and difference responses, in which the signals from the two elements of the loop pair are added and subtracted, respectively. The former response shows little variation as the beam or wire is displaced from the midplane of the loop-pair; the latter exhibits a roughly linear variation with displacement, and is used to detect the position variation of the particles in cooling systems. In general, the beam and wire measurements were found to be in excellent agreement.
Date: May 1, 1985
Creator: Goldberg, D.A.; Lambertson, G.R.; Voelker, F. & Shalz, L.
Partner: UNT Libraries Government Documents Department

Comparison between theoretical predictions and tracking

Description: The beam-beam interaction in a proton-antiproton collider has been an outstanding issue for a long time. Several theoretical predictions have been made in the past which range from the appearance of single beam-beam driven resonances to the onset of stochasticity and Arnold diffusion and the presence of chaotic trajectories. All these effects would cause a limit on the maximum strength of the beam-beam interaction, the so called beam-beam tune-shift, and speculative values have been offered ranging from as low as 0.0005 to as large as a fraction of unit. The lower limit could be caused in a more complicated situation where the external focussing forces which keep the two beams in the same storage ring are also modulated in time. These theoretical predictions have been compared with extensive computer tracking where the motion of the particles is followed turn after turn over very long periods of time. Though it is indeed possible to observe the formation of several resonances, nevertheless the onset of connected stochasticity seems to occur at too large beam-beam tune-shift to be of any practical relevance. Moreover no Arnold diffusion has been observed to have any practical significance. Chaotic trajectories have been found to embed the phase space in disconnected regions of appreciable extension. They increase in numbers considerably when time modulation of external focussing forces is added. 15 refs., 18 figs.
Date: January 1, 1985
Creator: Ruggiero, A.G.
Partner: UNT Libraries Government Documents Department

pp Interaction Regions. [Superconducting super collider]

Description: This group served as the interface between experimenters and accelerator physicists. A start was made on a portfolio of IR's, building on previous studies including the Reference Designs Study (RDS). The group also looked at limits on time structure and luminosity, the clustering of IR's, external beams of secondary particles from the IR's, and various operational issues connected with the IR's. Designs were developed for interaction regions for RDS-B (individual cryostats for two 5-T rings, separated by 60 cm vertically). For a fixed geometry, the quadrupoles have been tuned over a range to give a factor of 100 variation in ..beta..* (1 to 100 m) and thus in luminosity; an even larger variation may well be possible. Variation of the minimum ..beta..* with free space between the quadrupole triplets, for a quad strength of 280 T/m and under the constraint of fixed chromaticity, showed a factor of five decrease in maximum luminosity in going from a high luminosity region with +-20 m free space to a small-angle region with +-100 m. Similar variants of the RDS-A IR were also found.
Date: January 1, 1984
Creator: Diebold, R. & Johnson, D.E.
Partner: UNT Libraries Government Documents Department

Power combiners/dividers for loop pickup and kicker arrays for FNAL stochastic cooling rings

Description: The anti-proton accumulator and debuncher at FNAL will use stochastic methods to ''cool'' the beam. Pairs of quarter-wavelength directional-coupler loops are used to detect and kick the beam. The loops are copper plates which are flush with the upper and lower wall of a rectangular beam pipe. The plates, when surrounded by a properly sized pocket, form a 100-ohm transmission-line directional coupler. As the beam passes, a signal which gives position and time information, is induced in the plates. But, because the signal levels are low (<.5 picowatts per pair), a power combiner (usually several primary combiners feeding a secondary combiner) is used to combine the outputs of many loops. Subsequently, the combined signal is amplified, filtered and then fed into a divider, (that is, a combiner operating in reverse). The divider distributes the signal into a different set of loops which modify (kick) the beam's position. Since the loop couplers are arranged linearly, in arrays of various lengths, combiners also provide a convenient method of reducing the number of vacuum feedthroughs and preamplifiers and their related costs in performance and dollars. In this note we describe various stripline combiner systems that add the outputs of 4, 8, 16 or 32 loops.
Date: May 1, 1985
Creator: Johnson, J.K. & Nemetz, R.
Partner: UNT Libraries Government Documents Department

Electron cooling of high energy beams

Description: A short note is presented to clarify the relationship between electron cooling time and beam energy and also to see how the nature of the electron beam enters. In particular, whether it is electron total current or current density that is significant is considered. There is no attempt to include any measure of sophistication, such as the effect of a solenoid field, but simply to use Coulomb scattering and statistical equilibrium. For simplicity, the 3 phase spaces (horizontal, vertical and momentum) are taken to have equal occupied areas, and the terminology for the transverse case is used. It appears from the analysis that it is impractical to consider using electron cooling at high energies for the purpose of cooling and accumulating antiprotons. However, if we already have ''cold'' proton and antiproton beams, it might be conceivable to use electron beams from storage rings for the purpose of sustaining constant luminosity and perhaps limiting beam loss and, therefore, background.
Date: January 1, 1978
Creator: Month, M.
Partner: UNT Libraries Government Documents Department

Anti p-p collider group

Description: While this small group was largely occupied in interacting with other groups, there are some conclusions of general interest. The anti p-p lattice and beam avoidance scheme for a single ring collider, as presented by T. Collins, was accepted as a proof-by-example that a collider could be built with a substantial luminosity. There were no suggestions for improvement, in fact the limitations of this design are not likely to be improved. A production rate of 10/sup 9/ anti p's/sec provides for a total luminosity of 3 x 10/sup 33/ or 5 x 10/sup 32/ in each of six interaction regions.
Date: January 1, 1984
Creator: Collins, T.; Gelfand, N.; Johnson, D.; Walker, J.; Diebold, R. & Frisch, H.
Partner: UNT Libraries Government Documents Department

Antiproton acceleration in the Fermilab Main Ring and Tevatron

Description: The operation of the Fermilab Main Ring and Tevatron rf systems for colliding beams physics is discussed. The changes in the rf feedback system required for the accelration of antiprotons, and the methods for achieving proper transfer of both protons and antiprotons are described. Data on acceleration and transfer efficiencies are presented.
Date: March 1, 1987
Creator: Martin, P.; Dinkel, J.; Ducar, R.; Kerns, C.; Kerns, Q.; Meisner, K. et al.
Partner: UNT Libraries Government Documents Department

Antiproton source beam position system

Description: The TeV I Beam Position Monitor (BPM) system is designed to provide a useful diagnostic tool during the commissioning and operational phases of the antiproton source. Simply stated the design goal is to provide single turn position information for intensities of > 1x10/sup 9/ particles, and multi-turn (clocked orbit) information for beam intensities of > 1x10/sup 7/ particles, both with sub-millimeter resolution. It is anticipated that the system will be used during commissioning for establishing the first turn through the Debuncher and Accumulator, for aligning injection orbits, for providing information necessary to correct closed orbits, and for measuring various machine parameters (e.g. tunes, dispersion, aperture, chromaticity). During normal antiproton operation the system will be used to monitor the beam position throughout the accumulation process.
Date: May 1, 1984
Creator: Bagwell, T.; Holmes, S.; McCarthy, J. & Webber, R.
Partner: UNT Libraries Government Documents Department

Pbar Source Group summary

Description: Maxium antiproton accumulation rates have been investigated. A scheme is outlined which would accumulate more than 7E8 pbars/s ina form suitable for a peak luminosity of more than 0.5E33 /(s*cm**2) in a single SSC ring. This scheme utilizes only moderate extrapolations of present technology. Each of the stages in the accumulation process has been investigated in some detail with the same calculational tools as have been used in the CERN and Fermilab pbar sources. The results of these calculations and possibilities for improvements are discussed.
Date: January 1, 1984
Creator: Johnson, R.P. & Simpson, J.
Partner: UNT Libraries Government Documents Department