174 Matching Results

Search Results

Advanced search parameters have been applied.

Procedures for Deceleration Studies

Description: The purpose of deceleration studies is to construct the deceleration ramp files that are used to decelerate antiproton beam for experiment E835. A deceleration ramp file is a set of ramp tables that are downloaded to PAUX (a part of the Pbar front end) prior to a deceleration. There is a ramp table for each device that is changed during a deceleration. These tables determine how PAUX changes each device setting during a deceleration. Appendix 1 gives a table of all ramped devices. Presently a deceleration to the lowest energy allowed by our ramps requires the use of three ramp files: the first decelerates the beam from 8801 MeV/c to 6367 MeV/c, the second from 6367 MeV/c to 4858 MeV/c, and the third from 4858 MeV/c to 3900 MeV/c. At the time of this writing the third ramp file has yet to be completed. An important new feature of the present deceleration ramp files is that the value of {gamma}{sub t} is decreased as the beam is decelerated so that the Accumulator is always above transition.
Date: November 5, 1999
Creator: Werkema, Steve
Partner: UNT Libraries Government Documents Department

Impedances and beam stability issues of the Fermilab recycler ring

Description: The Fermilab Recycler Ring (permanent magnets) will be built on top of the Fermilab Main Injector sharing the same tunnel; its main function is to recycle the anti-protons after a store in the Tevatron and to provide storage for them after after accumulation and cooling in the Accumulator. Estimates of coupling impedances show domination by space charge. Examination of longitudinal instabilities shows that microwave instability will not occur if there are only N = 2.53 x 10{sup 12} anti-protons in the beam. Longitudinal coupling-bunch instability during injection stacking does not appear possible because of long bunch lengths/short bunch gaps and lack of sharp resonances. Transverse instability, on the other hand, cannot be Landau damped by the momentum spread in the beam, but it can be cured by a small spread in the betatron tunes (either from space charge or an octupole).
Date: April 1, 1996
Creator: Ng, King-Yuen
Partner: UNT Libraries Government Documents Department

``Electron Lens`` to Compensate Bunch-to-Bunch Tune Spread in TEV33

Description: In this article we discuss an electron beam lens for compensation of bunch-to-bunch tune spread in the Tevatron antiproton beam. Time-modulated current of an electron beam can produce defocusing forces necessary to compensate effects caused by parasitic beam-beam interactions with proton beam. We estimate maim parameters of the electron beam and consider resulting beam footprint. Emittance growth rate due to the electron current fluctuations is discussed.
Date: October 1, 1997
Creator: Shiltsev, V.
Partner: UNT Libraries Government Documents Department

Ion trapping in Recycler Ring

Description: Transverse instabilities have been observed in the antiproton beam stored in the Fermilab Recycler Ring, resulting in a sudden increase in the transverse emittances and a small beam loss. The instabilities appear to occur a few hours after a change in the ramping pattern of the Main Injector which shares the same tunnel. The phenomena have been studied by inducing similar instabilities. However, the mechanism is still unknown. A possible explanation is that the ions trapped in the beam reach such an intensity that collective coupled transverse oscillation occurs. However, there is no direct evidence of the trapped ions at this moment.
Date: June 28, 2004
Creator: Ng, K.Y.
Partner: UNT Libraries Government Documents Department

Antiproton Interaction Cross Sections

Description: Using the 1.19-Bev/c antiproton beam recently discovered at the Berkeley Bevatron of the University of California, we have measured the attenuation cross section in beryllium and copper. These cross sections are compared to attenuation measurements made with the same geometry using positive protons of the same incident energy (497 MeV).
Date: February 27, 1956
Creator: Chamberlain, Owen; Keller, Donald V.; Segre, Emilio; Steiner,Herbert M.; Wiegand, Clyde & Ypsilantis, Tom
Partner: UNT Libraries Government Documents Department

Transverse instability of the antiproton beam in the Recycler Ring

Description: The brightness of the antiproton beam in Fermilab's 8 GeV Recycler ring is limited by a transverse instability. This instability has occurred during the extraction process to the Tevatron for large stacks of antiprotons even with dampers in operation. This paper describes observed features of the instability, introduces the threshold phase density to characterize the beam stability, and finds the results to be in agreement with a resistive wall instability model. Effective exclusion of the longitudinal tails from Landau damping by decreasing the depth of the RF potential well is observed to lower the threshold density by up to a factor of two.
Date: March 1, 2011
Creator: Prost, L.R.; Bhat, C.M.; Burov, A.; Crisp, J.; Eddy, N.; Hu, M. et al.
Partner: UNT Libraries Government Documents Department


Description: A 0.1-0.5 A, 4.3 MeV DC electron beam provides cooling of 8 GeV antiprotons in Fermilab's Recycler storage ring. The most detailed information about the cooling properties of the electron beam comes from drag rate measurements. We find that the measured drag rate can significantly differ from the cooling force experienced by a single antiproton because the area of effective cooling is significantly smaller than the physical size of the electron beam and is comparable with the size of the antiproton beam used as a probe. Modeling by the BETACOOL code supports the conclusion about a large radial gradient of transverse velocities in the presently used electron beam.
Date: September 10, 2007
Partner: UNT Libraries Government Documents Department

Performance of the Fermilab's 4.3 MeV electron cooler

Description: A 4.3 MeV DC electron beam is used to cool longitudinally an antiproton beam in the Fermilab's Recycler ring. Cooling capabilities of the electron beam are characterized by the drag rate that was measured at various conditions. Fitting the results with a formula for non-magnetized cooling gives electron parameters that agree within a factor of 2 with independently measured electron beam properties.
Date: June 1, 2006
Creator: Shemyakin, A.; Burov, Alexey V.; Carlson, K.; Hu, M.; Kroc, T.; Leibfritz, J. et al.
Partner: UNT Libraries Government Documents Department

Beam-beam effects in the Tevatron

Description: The Tevatron in Collider Run II (2001-present) is operating with 6 times more bunches, many times higher beam intensities and luminosities than in Run I (1992-1995). Electromagnetic long-range and head-on interactions of high intensity proton and antiproton beams have been significant sources of beam loss and lifetime limitations. We present observations of the beam-beam phenomena in the Tevatron and results of relevant beam studies. We analyze the data and various methods employed in operations, predict the performance for planned luminosity upgrades, and discuss ways to improve it.
Date: January 1, 2005
Creator: Shiltsev, V.; Alexahin, Y.; Lebedev, V.; Lebrun, P.; Moore, R.S.; Sen, T. et al.
Partner: UNT Libraries Government Documents Department

Relativistic Stern-Gerlach Interaction in an RF Cavity

Description: The general expression of the Stern-Gerlach (SG) force is deduced for a relativistic charged spin-1/2 particle which travels inside a time varying magnetic field. This result was obtained either by means of two Lorentz boosts or starting from Dirac's equation. Then, the utilization of this interaction for attaining the spin states separation is reconsidered in a new example using a new radio-frequency arrangement. On the basis of the previous estimates, we feel ready to propose the time varying SG interaction as a method for attaining a spin state separation of an unpolarized beam of, say (anti)protons, since the energy of particles with opposite spin orientations will differ and beams in the two states can be separated. In a first stage of the study of a sensible practical design, we intend to proceed with numerical simulations. As a first step, we intend to verify the correctness of Eqs.(42) and (43) setting once {beta}{sub ph} = 2 and then {beta}{sub ph} = 3, in a cavity where the field line pattern can be realistically controlled. Beyond the verification of the present theory, there is also the aim of studying the effects generated by the spin precession inside the cavity, that we did not yet address in this note. Next, we shall consider a spin splitter scheme based on the lattice of an existing or planned (anti)proton ring endowed with an array of splitting cavities. The principal aim of the latter implementations is to check the mixing effect of the longitudinal phase-plane filamentation, i.e. the actual foe which could frustrate the entire spin splitting process.
Date: May 1, 2009
Creator: Conte,M.; Luccio, A. U. & Pusterla, M.
Partner: UNT Libraries Government Documents Department

An Updated AP2 Beamline TURTLE Model

Description: This note describes a TURTLE model of the AP2 beamline. This model was created by D. Johnson and improved by J. Hangst. The authors of this note have made additional improvements which reflect recent element and magnet setting changes. The magnet characteristics measurements and survey data compiled to update the model will be presented. A printout of the actual TURTLE deck may be found in appendix A.
Date: August 23, 1991
Creator: Gormley, M. & O'Day, S.
Partner: UNT Libraries Government Documents Department

Measurement of Trapped Ion Pockets and Control of Ion Instabilities in the Fermilab Antiproton Accumulator

Description: Resonant interaction of positively charged, trapped residual gas ions with a negatively charged, intense antiproton beam has been identified as the primary cause of transverse instability in the Fermilab antiproton accumulator. An upgraded ion clearing system was recently installed. This upgrade yielded a significant improvement in machine performance as well as an enhanced capability for studying trapped ion related phenomena. The operational impact and preliminary results from some initial measurements made with this system are presented herein.
Date: January 1, 1993
Creator: Werkema, Steven J.; Fullett, Kenneth D.; Zhou, Ping & /Fermilab
Partner: UNT Libraries Government Documents Department

Precision Measurement of the Accumulator Beam Energy

Description: The Antiproton Source Accumulator has been used by Fermilab experiments E760 and E835 to search for and measure the various states of charmonium below the open charm threshold. Accurate determination of the resonance parameters (mass, width, and branching ratios) of these states requires a precise measurement of the antiproton beam energy. The purpose of this report is to give a detailed description of the method that is used to accomplish a precision measurement of the antiproton beam energy.
Date: February 28, 2000
Creator: Werkema, Steven J.
Partner: UNT Libraries Government Documents Department

Status of the Fermilab Recycler

Description: The author presents the current operational status of the Fermilab Recycler Ring. Using a mix of stochastic and electron cooling, we prepare antiproton beams for the Fermilab Tevatron Collider program. Included are discussion of stashing and cooling performance, operational scenarios, and collider performance.
Date: September 1, 2007
Creator: Derwent, P.F.
Partner: UNT Libraries Government Documents Department

Overview of coupled bunch active damper systems at FNAL

Description: Beam intensities in all of the accelerators at Fermilab will increase significantly when the Main Injector becomes operational and will cause unstable oscillations in transverse position and energy. Places where the coupled bunch oscillations could dilute emittances include the Booster, Main Injector, and Tevatron. This paper provides an overview of the active feedback system upgrades which will be used to counteract the problem. It will explain the similarities between all the systems and will also explain design differences between longitudinal and transverse systems, fast sweeping systems, and systems for partially filled machines. Results from operational systems will also be shown. 7 refs., 4 figs., 1 tab.
Date: May 1, 1996
Creator: Steimel, J.; Crisp, J.; Ma, Hengjie; Marriner, J. & McGinnis, D.
Partner: UNT Libraries Government Documents Department

A new antiproton beam transfer scheme without coalescing

Description: An effective way to increase the luminosity in the Fermilab Tevatron collider program Run2 is to improve the overall antiproton transfer efficiency. During antiproton coalescing in the Main Injector (MI), about 10-15% particles get lost. This loss could be avoided in a new antiproton transfer scheme that removes coalescing from the process. Moreover, this scheme would also eliminate emittance dilution due to coalescing. This scheme uses a 2.5 MHz RF system to transfer antiprotons from the Accumulator to the Main Injector. It is then followed by a bunch rotation in the MI to shorten the bunch length so that it can be captured by a 53 MHz RF bucket. Calculations and ESME simulations show that this scheme works. No new hardware is needed to implement this scheme.
Date: June 4, 2003
Creator: al., Weiren Chou et
Partner: UNT Libraries Government Documents Department

Antiproton stacking and un-stacking in the Fermilab Recycler Ring

Description: The Fermilab Recycler Ring (RR) is intended to be used as a future antiproton storage ring for the Run II proton-antiproton collider operation. It is proposed that about 40mA of antiproton beam from the Accumulator Ring will be transferred to the Recycler once for every two to three hours, stacked and cooled. This operation continues for about 10 to 20 hours depending on the collider needs for antiprotons. Eventually, the cooled antiproton beam will be un-stacked from the Recycler and transferred to the Tevatron via the Main Injector. They have simulated stacking and un-stacking of antiprotons in the Recycler using multi-particle beam dynamics simulation code ESME. In this paper they present results of these simulations.
Date: June 12, 2003
Creator: Bhat, Chandra
Partner: UNT Libraries Government Documents Department

Longitudinal emittance measurements in the Fermilab Recycler Ring

Description: The Recycler Ring (RR) is a new 8Gev antiproton storage ring at Fermilab. Presently, this machine is being commissioned using protons from the Booster. It uses barrier buckets for stacking, un-stacking and storing the beam. At any given time, the RR is capable of storing proton or antiproton beams in multiple segments azimuthally. These segments of the beam may have widely differing longitudinal emittance and beam intensities and bunch lengths. It is highly essential to be able to measure the longitudinal emittance and keep track of the longitudinal dynamics at various stages of the operation of the RR. In this paper, the authors discuss a few methods of longitudinal emittance measurements in barrier buckets and discuss their merits and demerits
Date: June 10, 2003
Creator: Bhat, C. M. & Marriner, John P.
Partner: UNT Libraries Government Documents Department

Prospectus for an electron cooling system for the recycler

Description: The Recycler ring was added to the Main Injector (MI) project in 1997 as means to recover the antiprotons remaining at the end of Tevatron stores and to serve as a second stage accumulator to raise the maximum stack current. This report describes an electron cooling system with substan-tially higher stack capacity than the Recycler stochastic cooling system which could be brought into operation toward the end of Run II. It is the major component of a program to double the de-sign Run II luminosity and should have a positive effect on integrated luminosity soon after turn-on. The upgrade potential is intended to meet the longer term needs of the Laboratory�s luminosity upgrade program. The current experience with electron cooling is discussed to provide the ratio-nale for the choice of design parameters and to make clear the needs for additional development work. Both analytical and numerical development of the theory has been pursued to confirm that the limits in principle are well beyond foreseen need. The specific hardware described is not the only realization that has been considered, but it is in some ways the most conservative. The gen-eral scheme of using an electrostatic accelerator with high efficiency charge recovery was actively discussed in the 1980�s. Recent developments have served to build confidence in this approach, but, by whatever means realized, a Recycler electron cooling system will require significant extension of current practice. The Prospectus incorporates the ideas and understanding current 15 September 1998. Rapid progress toward a comprehensive development plan at this time means that its details will already differ from ideas now current.
Date: November 1, 1998
Creator: J.A. MacLachlan, Editor
Partner: UNT Libraries Government Documents Department

Spin states separation based on the longitudinal Stern-Gerlach effect

Description: Repetitive longitudinal impulses of the Stern-Gerlach force are proposed for attaining the separation of the opposite spin states of (anti)proton beams, circulating either in existing collider facilities or in a small ring, conceived just for producing polarized antiprotons at very low energy. After a brief presentation of the theoretical background which supports this proposal, the experimental features are discussed emphasizing in particular the bunch separation within the RF bucket and the feasibility of a high magnetic gradient TE cavity.
Date: December 1, 1996
Creator: Akchurin, N.; Conte, M. & MacKay, W.W.
Partner: UNT Libraries Government Documents Department

Fermilab R{ampersand}D program in medium energyelectron cooling

Description: Fermilab began an R & D program in medium energy electron cooling in April 1995 with the object of cooling 8 GeV antiprotons in a new 3.3 km permanent magnet storage ring (Recycler) to be built in the same tunnel as the Main Injector (MI). The MI is to be completed in 1998, and it is planned to install the Recycler by the end of 1997 to reduce interference during the final rush of MI installation. Although the Recycler will employ stochastic cooling initially, its potential for contributing an order of magnitude to Tevatron collider luminosity is tied to electron cooling. The short time scale and Fermilab`s limited familiarity with low energy electron beams has given rise to a two-phase development plan. The first phase is to build a cooling system based on an electron beam of {ge} 200 mA before year 2000. The second phase of about 3 years is planned to reach electron current of 2 A or more. This report describes the general scheme for high luminosity collider operation as well as the R & D plan and progress to date. 17 refs., 5 figs., 1 tab.
Date: July 1, 1996
Creator: MacLachlan, J.A.
Partner: UNT Libraries Government Documents Department

Contributions to the second workshop on medium energy electron cooling - MEEC96

Description: MEEC96 was a workshop devoted primarily to discussion within four working groups, not a mini-conference of prepared reports. Therefore, although there are contributions bearing the name of a single author, much of what was learned came in extemporaneous discussion of the issues posed to the participants. The original plan to produce formal proceedings has been dropped because of the limited number of participants willing to write up their own contributions and because of the difficulty of converting free-wheeling discussion to the written word. The premsise for the 1996 gathering was to set a critique of Fermilab`s R&D effort at cooling a ring of 8 GeV {bar p}`s. Separate abstracts have been submitted to the energy database for contributions to this workshop.
Date: September 1, 1997
Creator: MacLachlan, J.
Partner: UNT Libraries Government Documents Department

Fast PIN-diode beam loss monitors at Tevatron

Description: The article is devoted to results of fine time structure of particle losses in Tevatron with use of fast beam loss monitors (BLM) based on PIN-diodes. An ultimate goal of the new BLMs is to distinguish losses of protons and antiprotons from neighbor bunches with 132 ns bunch spacing in the Tevatron collider upgrade. The devices studied fit well to the goal as they can recognize even seven times closer - 18.9 ns - spaced bunches` losses in the Tevatron fixed target operation regime. We have measured main characteristics of the BLM as well as studied the proton losses over 10 decades of time scale - from dozen of minutes to dozen of nanoseconds. Power spectral density of the losses is compared with spectra of the proton beam motion.
Date: July 1, 1997
Creator: Shiltsev, V.
Partner: UNT Libraries Government Documents Department