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in subjects: "Stability Accelerators"

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Trapped Ions and Beam Coherent Instability

In accelerators with negatively charged beams, ions generated from the residual gas molecules may be trapped by the beam. Trapped ions may interact resonantly with the beam and cause a beam-ion coherent instability. This coherent instability bears many similarities to the resistive wall instability and can present important limitations to those machines operation. A description of this effect requires a treatment of the beam coherent instability including both the normal machine wake field and … more

Date: January 1, 1992

Creator: Zhou, P.; Colestock, P. L. & Werkema, S. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Chromaticity and impedance effect on the transverse motion of longitunial bunch slices in the Tevatron

The Transverse turn-by-turn evolution of a bunch slice is examined considering chromatic and impedance effects. A quasi-analytical approximation is developed using perturbative expansion of Hill's equation with a wake field. This approximation is compared to turn-by-turn measurements taken in the Tevatron and from this linear and second order chromaticity, and impedance are calculated as well as beam stability thresholds.

Date: May 1, 2005

Creator: Ranjbar, V. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Landau damping of the weak head-tail instability at Tevatron

Two-step improvement of transverse beam stability has been done at the Tevatron. First, shielding of the laminated Lambertson magnets significantly reduced the transverse impedance. Second, Landau damping induced by the octupoles allowed machine operation with zero chromaticity at injection. That has resulted in a dynamic aperture increase and weakening of long-range beam-beam effects due to smaller chromatic tune modulation. At collisions, the coherent tunes and incoherent tune continuum are s… more

Date: May 1, 2005

Creator: Ivanov, P. M.; Alexahin, Y.; Annala, J.; Lebedev, V. A. & Shiltsev, V.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

NuMI proton kicker extraction magnet termination resistor system

The temperature stability of the kicker magnet termination resistor assembly directly affects the field flatness and amplitude stability. Comprehensive thermal enhancements were made to the existing Main Injector resistor assembly design to satisfy NuMI performance specifications. Additionally, a fluid-processing system utilizing Fluorinert{reg_sign} FC-77 high-voltage dielectric was built to precisely control the setpoint temperature of the resistor assembly from 70 to 120F, required to mainta… more

Date: May 1, 2005

Creator: Reeves, S. R. & Jensen, C. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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NuMI proton kicker extraction system

This system extracts up to 9.6 {micro}s of 120 GeV beam every 1.87 seconds for the NuMI beamline neutrino experiments. A pulse forming network consisting of two continuous wound coils and 68 capacitors was designed and built to drive three kicker magnets. The field stability requirement is better than {+-} 1% with a field rise time of 1.52 {micro}s. New kicker magnets were built based on the successful traveling wave magnets built for the Main Injector. Two of these magnets are in series which … more

Date: May 1, 2005

Creator: Jensen, C. C. & Krafczyk, G. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Tevatron Beam-Beam Compensation Project Progress

In this paper, we report the progress of the Tevatron Beam-Beam Compensation (BBC) project [1]. Electron beam induced proton and antiproton tuneshifts have been reported in [2], suppression of an antiproton emittance growth has been observed, too [1]. Currently, the first electron lens (TEL1) is in operational use as the Tevatron DC beam cleaner. We have made a lot of the upgrades to improve its stability [3]. The 2nd Tevatron electron lens (TEL2) is under the final phase of development and pre… more

Date: May 1, 2005

Creator: Shiltsev, V.; Zhang, X. L.; Kuznetsov, G.; Pfeffer, H.; Saewert, G.; Zimmermann, F. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Measurement of critical current and instability threshold of rutherford-type nb3sn cables

As part of a collaboration between FNAL and CERN, Nb{sub 3}Sn Rutherford-type cables made of different wires (MJR and PIT) have been assembled in the sample holder at FNAL and tested at FRESCA (CERN). All cable samples had 28 strands with 1-mm diameter, and a trapezoidal cross-section with 0.9-1 degree keystone angle. All samples were tested at 4.3 and 1.8 K. After the first series of tests both cables were retested with higher prestress. The PIT sample was extensively retested at 1.9 K. During… more

Date: December 1, 2005

Creator: Ambrosio, G.; Andreev, N.; Barzi, E.; Bordini, B.; Denarie, C. -H.; Verweij, A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Rotating Coil Apparatus with Sub-Micrometer Magnetic Center Measurement Stability

A rotating double coil apparatus has been designed and built so that the relative magnetic center change of a quadrupole is measured to an uncertainty smaller than 0.02 micrometers (=micron, {micro}m) for a single measurement. Furthermore, repeated measurements over about an hour vary by less than 0.1 {micro}m and by less than 1 {micro}m for periods of 24 hrs or longer. Correlation analyses of long data runs show that the magnet center measurement is sensitive to mechanical effects, such as vib… more

Date: December 2, 2005

Creator: Spencer, Cherrill M.; Anderson, Scott D.; Jensen, David R. & Wolf, Zachary R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Issues of Stability and Ground Motion in ILC

Stability of International Linear Collider is determined by the stability of the site, additional noises of beamline component, energy and kicker jitter, and performance of train-to-train and intratrain feedback. Stability goals in terms of the beam jitter at the end of the linac, in BDS and at the IP are discussed in this paper, and translated to stability goals for the site and for component jitter. Present status of stability studies is reviewed and feasibility of achieving the stability goa… more

Date: February 3, 2006

Creator: Seryi, Andrei; Hendrickson, Linda & White, Glen

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Field Quality And Magnetic Center Stability Achieved in a Variable Permanent Magnet Quadrupole for the ILC

A superstrong permanent magnet quadrupole (PMQ) is one of the candidates for the final focus lens for the International Linear Collider (ILC). Our prototype PMQ can produce variable strengths from 3.5T to 24.2T in 1.4T steps. The magnetic center of the PMQ must not move more than a few microns during a 20% strength change to enable a Beam-Based Alignment (BBA) process to work. Our PMQ can be mechanically adjusted to suppress the center movement from more than 30{micro}m to less than 10{micro}m … more

Date: February 6, 2006

Creator: Iwashita, Y.; Mihara, T.; Kumada, M. & Spencer, C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Linearizing Intra-Train Beam-Beam Deflection Feedback

Beam-beam deflection feedback acting within the crossing time of a single bunch train may be needed to keep linear collider beams colliding at high luminosity. In a short-pulse machine such as the Next Linear Collider (NLC) this feedback must converge quickly to be useful. The non-linear nature of beam-beam deflection vs. beam-beam offset in these machines precludes obtaining both rapid convergence and a stable steady-state lock to beam offsets with a linear feedback algorithm. We show that a s… more

Date: February 22, 2006

Creator: Smith, S. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

ATF2 Proposal Volume 2

For achieving the high luminosity required at the International Linear Collider (ILC), it is critical to focus the beams to nanometer size with the ILC Beam Delivery System (BDS), and to maintain the beam collision with a nanometer-scale stability. To establish the technologies associated with this ultra-high precision beam handling, it has been proposed to implement an ILC-like final focus optics in an extension of the existing extraction beamline of ATF at KEK. The ATF is considered to be the… more

Date: February 27, 2006

Creator: Grishanov, B.I.; Logachev, P.; Podgorny, F.; Telnov, V.; /Novosibirsk, IYF; Angal-Kalinin, D. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Beam Instrumentation Challenges at the International Linear Collider

The International Linear Collider (ILC) is a proposed facility for the study of high energy physics through electron-positron collisions at center-of-mass energies up to 500 GeV and luminosities up to 2 x 10{sup 34} cm{sup -2} sec{sup -1}. Meeting the ILC's goals will require an extremely sophisticated suite of beam instruments for the preservation of beam emittance, the diagnosis of optical errors and mismatches, the determination of beam properties required for particle physics purposes, and … more

Date: May 16, 2006

Creator: Tenenbaum, Peter

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Coherent instabilities at the FNAL Booster

This paper presents results of experimental and theoretical investigations of transverse beam stability at injection to Fermilab Booster and discusses a novel scheme for transition crossing allowing to avoid the longitudinal emittance growth related to the transition. At reduced chromaticity a multibunch high order head-tail mode develops with growth time of 12 turns at fractional part of tune close to zero. An estimate of the growth rate based on known sources of impedance results in significa… more

Date: June 1, 2006

Creator: Lebedev, V.; Burov, A.; Pellico, W.; Yang, X. & /Fermilab

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

On possible use of electron lenses in LHC

We present basic facts about electron lenses used in high-energy accelerators and discuss their possible application in the LHC. Four proposals are presented: (a) electron lenses for compensation of head-on beam-beam effects; (b) electron lens as tune-spreader for better beam stability; (c) as electromagnetic primary collimator for ions and protons; (d) satellite bunch cleaning by electron lenses. Main requirements are discussed.

Date: October 1, 2006

Creator: Shiltsev, V.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Study of Laser System Requirements for Application in Beam Diagnostics And Polarimetry at the ILC

Advanced laser systems will be essential for a range of diagnostics devices and polarimetry at the ILC. High average power, high beam quality, excellent stability and reliability will be crucial in order to deliver the information required to attain the necessary ILC luminosity as well as for efficient polarimetry. The key parameters are listed together with the R & D required to achieve the necessary laser system performance.

Date: February 12, 2007

Creator: Dixit, S.; Delerue, N.; Foster, B.; Howell, D. F.; Peach, K.; Quelch, G. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Toroidal Charge Monitor for High-Energy Picosecond Electron Beams

A monitor system suitable for the accurate measurement of the total charge of a 2-ps 28.5 GeV electron beam over a large dynamic range is described. Systematic uncertainties and results on absolute calibration, resolution, and long-term stability are presented.

Date: March 28, 2007

Creator: Simmons, Robert H. & Ng, Johnny S.T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Stability of A-150 plastic ionization chamber response over a ~30 year period

At the NIU Institute for Neutron Therapy at Fermilab, the clinical tissue-equivalent ionization chamber response is measured every treatment day using a cesium source that was configured to match readings obtained at the National Bureau of Standards. Daily measurements are performed in air using the air-to-tissue dose conversion factors given in AAPM Report no. 7. The measured exposure calibration factors have been tabulated and graphed as a function of time from 1978 to present. For A-150 plas… more

Date: August 1, 2007

Creator: Kroc, Thomas K. & Lennox, Arlene J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Cavity BPM System Tests for the ILC Spectrometer

The main physics program of the International Linear Collider (ILC) requires a measurement of the beam energy at the interaction point with an accuracy of 10{sup -4} or better. To achieve this goal a magnetic spectrometer using high resolution beam position monitors (BPMs) has been proposed. This paper reports on the cavity BPM system that was deployed to test this proposal. We demonstrate sub-micron resolution and micron level stability over 20 hours for a 1 m long BPM triplet. We find micron-… more

Date: December 21, 2007

Creator: Slater, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Optics implications of implementing Nb3Sn magnets in the LHC phase 1 upgrade

CERN has encouraged the US-LARP collaboration to participate in Phase I of the LHC luminosity upgrade by analyzing the benefits gained by using Nb3Sn technology to replace the functionality of select NbTi magnets that CERN is committed to construct. Early studies have shown that the much higher gradients (shorter magnetic lengths) and temperature margins (quench stability) of Nb3Sn magnets compared to their NbTi counterparts is favorable--allowing the insertion of additional absorbers between Q… more

Date: June 1, 2008

Creator: Johnstone, J. A.; Kashikhin, V. V.; Mokhov, N. V. & Zlobin, A. V.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Simulation of Wakefield Effect in ILC IR Chamber

To achieve super high luminosity, high current beams with very short bunch length are needed, which carry high intensity EM fields. For ILC, two bunch trains with bunch length of 300 {micro}m and bunch charge of 3.2nC are needed to collide at the IR to achieve the ILC luminosity goals. When the 300 {micro}m bunches pass through the IR chamber, wakefields will be excited, which will cause HOM power flowing through the IR chamber beam pipe to the final doublets due to the high frequency character… more

Date: June 26, 2008

Creator: Pei, S; Seryi, A. & Raubenheimer, T.O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Phase stability of a microtron driving a terahertz FEL

The phase stability of bunches accelerated by a magnetron-driven microtron-injector of a terahertz Free Electron Laser (FEL) has been studied to optimize the microtron regimes providing good operation of the FEL. The study is based on a simulation of the beam dynamics in the microtron considering 2-D motion of the electrons in the median plane. This allows the computation of the current loading the accelerating cavity as well as the output microtron current. The loading current has been used to… more

Date: August 1, 2008

Creator: Kazakevich, Grigory M.; Pavlov, Viatcheslav M.; Jeong, Young Uk & Lee, Byung Cheol

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Phase and Frequency Locked Magnetrons for SRF Sources

Magnetrons are low-cost highly-efficient microwave sources, but they have several limitations, primarily centered about the phase and frequency stability of their output. When the stability requirements are low, such as for medical accelerators or kitchen ovens, magnetrons are the very efficient power source of choice. But for high energy accelerators, because of the need for frequency and phase stability - proton accelerators need 1-2 degrees source phase stability, and electron accelerators n… more

Date: May 1, 2009

Creator: Neubauer, M.; Johnson, R. P.; Popovic, M. & Moretti, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Stability of Flat Bunches in the Recycler Barrier Bucket

We examine the stability of intense flat bunches in barrier buckets used in the Fermilab Recycler. We consider some common stationary distributions and show that they would be unstable against rigid dipole oscillations. We discuss the measurements which identify stable distributions. We also report on experimental studies on the impact of creating a local extremum of the incoherent frequency within the rf bucket. We considered two typical stationary distributions and found they were not adequat… more

Date: May 1, 2009

Creator: Sen, T.; Bhat, C. & Ostiguy, J. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department