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Tevatron run-II beam collimation system

Description: Based on realistic Monte-Carlo simulations a two-stage beam collimation system is designed to minimize the beam loss in the Fermilab Tevatron for fixed target and collider Run II. Thin primary collimators are used to increase particle amplitude and their impact parameter on the down-stream secondary collimators. This results in a significant reduction of the total beam loss in the machine, decreases collimator overheating and mitigates requirements to colli-mator alignment. A set of collimators will originally be in-stalled for fixed target operation and for antiprotonbeam re-cycling studies. The collimation system improvement will continue into the collider Run II and intensity upgrade.
Date: April 13, 1999
Creator: al., Michael Church et
Partner: UNT Libraries Government Documents Department

Beam losses due to abrupt crab cavity failures in the LHC

Description: A major concern for the implementation of crab crossing in a future High-Luminosity LHC (HL-LHC) is machine protection in an event of a fast crab-cavity failure. Certain types of abrupt crab-cavity amplitude and phase changes are simulated to characterize the effect of failures on the beam and the resulting particle-loss signatures. The time-dependent beam loss distributions around the ring and particle trajectories obtained from the simulations allow for a first assessment of the resulting beam impact on LHC collimators and on sensitive components around the ring. Results for the nominal LHC lattice is presented.
Date: March 28, 2011
Creator: Baer, T.; Barranco, J.; Calaga, R.; Tomas, R.; Wenninger, B.; Yee, B. et al.
Partner: UNT Libraries Government Documents Department

Lab-Based Measurement of Remediation Techniques for Radiation Portal Monitors (Initial Report)

Description: Radiation Portal Monitors (RPM) deployed by the Second Line of Defense (SLD) are known to be sensitive to the natural environmental radioactive background. There are several techniques used to mitigate the effects of background on the monitors, but since the installation environments can vary significantly from one another the need for a standardized, systematic, study of remediation techniques was proposed and carried out. This study is not meant to serve as the absolute last word on the subject. The data collected are, however, intelligible and useful. Some compromises were made, each of which will be described in detail. The hope of this initial report is to familiarize the SLD science teams with ORNL's effort to model the effect of various remediation techniques on simple, static backgrounds. This study provides a good start toward benchmarking the model, and each additional increment of data will serve to make the model more robust. The scope of this initial study is limited to a few basic cases. Its purpose is to prove the utility of lab-based study of remediation techniques and serve as a standard data set for future use. This importance of this first step of standardization will become obvious when science teams are working in parallel on issues of remediation; having a common starting point will do away with one category of difference, thereby making easier the task of determining the sources of disagreement. Further measurements will augment this data set, allowing for further constraint of the universe of possible situations. As will be discussed in the 'Going Forward' section, more data will be included in the final report of this work. Of particular interest will be the data taken with the official TSA lead collimators, which will provide more direct results for comparison with installation data.
Date: February 1, 2012
Creator: Livesay, Jake; Guzzardo, Tyler & Lousteau, Angela L
Partner: UNT Libraries Government Documents Department

50x50 GeV Muon Collider Beam Collimation

Description: A summary of different techniques and systems to scrape beam halo in a 50 x 50 GeV {mu}{sup +}{mu}{sup -} collider is presented. Such systems are installed in a special utility section with optics specifically designed to meet both the requirements of the scraping system and of injection. Results froma realistic Monte Carlo simulation (STRUCT-MARS) show that a system consisting of steel absorbers several meters in length suppresses halo-induced backgrounds in the collider detector by more than three orders of magnitude. The heat load in superconducting magnets near the scraper system can be reduced to tolerable levels by appropriate collimator design and location. This reduction applies to both injection and collider mode of operation. Also discussed is extraction of halo particles using electrostatic deflectors and bent crys-tals, although neither appears to be effective for a muon collider at this energy.
Date: April 14, 1999
Creator: Drozhdin, A. I.; Johnstone, C. J.; Mokhov, N. V.; Garen, A. A. & Biryukov, V. M.
Partner: UNT Libraries Government Documents Department


Description: For the year 2001 run, a bent crystal was installed in the yellow ring of the Relativistic Heavy Ion Collider (RHIC). The crystal forms the first stage of a two stage collimation system. By aligning the crystal to the beam, halo particles are channeled through the crystal and deflected into a copper scraper. The purpose is to reduce beam halo with greater efficiency than with a scraper alone. In this paper we present the first results from the use of the crystal collimator. We compare the crystal performance under various conditions, such as different particle species, and beta functions.
Date: June 2, 2002
Partner: UNT Libraries Government Documents Department

Precision monitoring of relative beam intensity for Mu2e

Description: For future experiments at the intensity frontier, precise and accurate knowledge of beam time structure will be critical to understanding backgrounds. The proposed Mu2e experiment will utilize {approx}200 ns (FW) bunches of 3 x 10{sup 7} protons at 8 GeV with a bunch-to-bunch period of 1695 ns. The out-of-bunch beam must be suppressed by a factor of 10{sup -10} relative to in-bunch beam and continuously monitored. I propose a Cerenkov-based particle telescope to measure secondary production from beam interactions in a several tens of microns thick foil. Correlating timing information with beam passage will allow the determination of relative beam intensity to arbitrary precision given a sufficiently long integration time. The goal is to verify out-of-bunch extinction to the level 10{sup -6} in the span of several seconds. This will allow near real-time monitoring of the initial extinction of the beam resonantly extracted from Fermilabs Debuncher before a system of AC dipoles and collimators, which will provide the final extinction. The effect on beam emittance is minimal, allowing the necessary continuous measurement. I will present the detector design and some concerns about bunch growth during the resonant extraction.
Date: April 1, 2011
Creator: Evans, N.J.; Kopp, S.E.; U., /Texas; Prebys, E. & /Fermilab
Partner: UNT Libraries Government Documents Department

Summary of working group g: beam material interaction

Description: For the first time, the workshop on High-Intensity and High-Brightness Hadron Beams (HB2010), held at Morschach, Switzerland and organized by the Paul Scherrer Institute, included a Working group dealing with the interaction between beam and material. Due to the high power beams of existing and future facilities, this topic is already of great relevance for such machines and is expected to become even more important in the future. While more specialized workshops related to topics of radiation damage, activation or thermo-mechanical calculations, already exist, HB2010 provided the occasion to discuss the interplay of these topics, focusing on components like targets, beam dumps and collimators, whose reliability are crucial for a user facility. In addition, a broader community of people working on a variety of issues related to the operation of accelerators could be informed and their interest sparked.
Date: November 1, 2010
Creator: Kiselev, D.; /PSI, Villigen; Mokhov, N.V.; /Fermilab; Schmidt, R. & /CERN
Partner: UNT Libraries Government Documents Department

Measurements of Transverse Beam Diffusion Rates in the Fermilab Tevatron Collider

Description: The transverse beam diffusion rate vs. particle oscillation amplitude was measured in the Tevatron using collimator scans. All collimator jaws except one were retracted. As the jaw of interest was moved in small steps, the local shower rates were recorded as a function of time. By using a diffusion model, the time evolution of losses could be related to the diffusion rate at the collimator position. Preliminary results of these measurements are presented.
Date: August 1, 2011
Creator: Stancari, G.; Annala, G.; Johnson, T.R.; Still, D.A.; Valishev, A. & /Fermilab
Partner: UNT Libraries Government Documents Department

Development of Nb3Sn 11 T single aperture demonstrator dipole for LHC upgrades

Description: The LHC collimation upgrade foresees additional collimators installed in dispersion suppressor regions. To obtain the necessary space for the collimators, a solution based on the substitution of LHC main dipoles for stronger dipoles is being considered. CERN and FNAL have started a joint program to demonstrate the feasibility of Nb{sub 3}Sn technology for this purpose. The goal of the first phase is the design and construction of a 2-m long single-aperture demonstrator magnet with a nominal field of 11 T at 11.85 kA with 20% margin. This paper describes the magnetic and mechanical design of the demonstrator magnet and summarizes its design parameters.
Date: March 1, 2011
Creator: Zlobin, A.V.; Apollinari, G.; Andreev, N.; Barzi, E.; Kashikhin, V.V.; Nobrega, f. et al.
Partner: UNT Libraries Government Documents Department

Loss Factor of Tapered Structures for Short Bunches

Description: Using the electromagnetic simulation code ECHO, we have found a simple phenomenological formula that accurately describes the loss factor for short bunches traversing an axisymmetric tapered collimator. In this paper, we consider tapered collimators with rectangular cross-section and use the GdfidL code to calculate the loss factor dependence on the geometric parameters for short bunches. The results for both axisymmetric and rectangular collimators are discussed. The behaviour of the impedance of tapered structures for very short bunches in the optical regime has been determined in refs. [10,11]. Here, for the loss factors for two particular geometries, we have studied the departure from the optical regime behaviour as bunch length is increased. In both cases, the ratio of the loss factor for the tapered collimator to the loss factor in the optical regime is a function only of the scaling parameter {sigma}L/d{sup 2}. The fact that the bunch length a and the taper length L appear as a product is consistent with the recent scaling derived by Stupakov in ref. [12], since there is only a weak dependence on g. One noteworthy fact that is not a priori expected is that only the larger radius or vertical half-aperture d appears. The reduction factor is independent of b. Moreover, it is striking that the specific form involving the arctan given in Eq. (5) holds for both geometries, with only the coefficient {mu} differing by a factor of {approx}2 for flat vs round. This suggests that there may be a useful phenomenological form for more general geometries which may follow from natural extensions of Eq. (5). This possibility is presently being investigated.
Date: March 28, 2011
Creator: Blednykh, A.
Partner: UNT Libraries Government Documents Department

Shortwave Spectroradiometer (SWS) Handbook

Description: The Shortwave Spectroradiometer (SWS), measures the absolute visible and near infrared spectralradiance (units of watts per meter square per nanometer per steradian) of the zenith directly above the instrument. The SWS is a moderate resolution sensor comprised of two Zeiss spectrometers (MMS 1 NIR enhanced and NIR-PGS 2.2) for visible and near-infrared detection in the wavelength range 350 – 2170 nm. The sampling frequency is 1 Hz. The spectral resolution is 8 nm for the MMS 1 NIR and 12 nm for the NIR-PGS 2.2. The light collector is a narrow field of view (1.4°) collimator at the front end of a high-grade custom-made fiber optic bundle. The SWS does daily daytime measurements. The SWS is located in a darkroom, constructed by Southern Great Plains (SGP) site personnel within the optical trailer, to permit calibrations to be conducted without the necessity of moving the instrument to a different location. Calibrations are performed at regularly scheduled times using the ARM 12” integrating sphere.
Date: November 1, 2006
Creator: Pilewskie, P & Pommier, J
Partner: UNT Libraries Government Documents Department

Optimization of the CLIC Baseline Collimation System

Description: Important efforts have recently been dedicated to the improvement of the design of the baseline collimation system of the Compact Linear Collider (CLIC). Different aspects of the design have been optimized: the transverse collimation depths have been recalculated in order to reduce the collimator wakefield effects while maintaining a good efficiency in cleaning the undesired beam halo; the geometric design of the spoilers have also been reviewed to minimize wakefields; in addition, the optics design have been polished to improve the collimation efficiency. This paper describes the current status of the CLIC collimation system after this optimization.
Date: July 6, 2012
Creator: Resta-Lopez, Javier; /Oxford U., JAI; Angal-Kalinin, Deepa; /Daresbury; Fernandez-Hernando, Juan; /Daresbury et al.
Partner: UNT Libraries Government Documents Department

Collimation system design for beam loss localization with slipstacking injection in the Fermilab Main Injector

Description: Results of modeling with the 3-D STRUCT and MARS15 codes of beam loss localization and related radiation effects are presented for the slipstacking injection to the Fermilab Main Injector. Simulations of proton beam loss are done using multi-turn tracking with realistic accelerator apertures, nonlinear fields in the accelerator magnets and time function of the RF manipulations to explain the results of beam loss measurements. The collimation system consists of one primary and four secondary collimators. It intercepts a beam power of 1.6 kW at a scraping rate of 5% of 5.5E+13 ppp, with a beam loss rate in the ring outside the collimation region of 1 W/m or less. Based on thorough energy deposition and radiation modeling, a corresponding collimator design was developed that satisfies all the radiation and engineering constraints.
Date: June 1, 2007
Creator: Drozhdin, A.I.; Brown, B.C.; Johnson, D.E.; Koba, K.; Kourbanis, I.; Mokhov, N.V. et al.
Partner: UNT Libraries Government Documents Department

Wakefields in the LCLS Undulator Transitions

Description: We have studied longitudinal wakefields of very short bunches in non-cylindrically symmetric (3D) vacuum chamber transitions using analytical models and the computer program ECHO. The wake (for pairs of well-separated, non-smooth transitions) invariably is resistive, with its shape proportional to the bunch distribution. For the example of an elliptical collimator in a round beam pipe we have demonstrated that--as in the cylindrically symmetric (2D) case--the wake can be obtained from the static primary field of the beam alone. We have obtained the wakes of the LCLS rectangular-to-round transitions using indirect (numerical) field integration combined with a primary beam field calculation. For the LCLS 1 nC bunch charge configuration we find that the total variation in wake-induced energy change is small (0.03% in the core of the beam, 0.15% in the horns of the distribution) compared to that due to the resistive wall wakes of the undulator beam pipe (0.6%).
Date: August 15, 2005
Creator: Bane, Karl L.F.; /SLAC; Zagorodnov, Igor A. & /DESY
Partner: UNT Libraries Government Documents Department

Wakefields in the LCLS Undulator Transitions

Description: For a short bunch in an elliptical collimator we demonstrate that, as in a purely round collimator, the wake can be estimated from the primary fields of the beam alone. We obtain the wakes in the LCLS rectangular-to-round, undulator transitions using a hybrid method that includes indirect numerical (field) integration and an analytical potential energy term. For the LCLS 1 nC bunch charge configuration, we find the wake-induced energy change in the transitions to be small compared to that due to the resistance of the beam pipe walls.
Date: July 17, 2006
Creator: Bane, K.L.F.; /SLAC; Zagorodov, I. & /DESY
Partner: UNT Libraries Government Documents Department

Beam Losses and Background Loads on Collider Detectors Due to Beam-Gas Interactions in the LHC

Description: With a fully-operational high-efficient collimation system in the LHC, nuclear interactions of circulating protons with residual gas in the machine beam pipe can be a major source of beam losses in the vicinity of the collider detectors, responsible for the machine-induced backgrounds. Realistic modeling of Coulomb scattering, elastic and inelastic interactions of 7-TeV protons with nuclei in the vacuum chamber of the cold and warm sections of the LHC ring--with an appropriate pressure profile--is performed with the STRUCT and MARS15 codes. Multi-turn tracking of the primary beams, propagation of secondaries through the lattice, their interception by the tertiary collimators TCT as well as properties of corresponding particle distributions at the CMS and ATLAS detectors are studied in great detail and results presented in this paper.
Date: April 1, 2009
Creator: Drozhdin, A.I.; Mokhov, N.V.; Striganov, S.I. & /Fermilab
Partner: UNT Libraries Government Documents Department

Machine-Related Backgrounds in the SiD Detector at ILC

Description: With a multi-stage collimation system and magnetic iron spoilers in the tunnel, the background particle fluxes on the ILC detector can be substantially reduced. At the same time, beam-halo interactions with collimators and protective masks in the beam delivery system create fluxes of muons and other secondary particles which can still exceed the tolerable levels for some of the ILC sub-detectors. Results of modeling of such backgrounds in comparison to those from the e{sup +}e{sup -} interactions are presented in this paper for the SiD detector.
Date: August 1, 2006
Creator: Denisov, D.S.; Mokhov, N.V.; Striganov, S.I.; /Fermilab; Kostin, M.A.; /Michigan State U., NSCL et al.
Partner: UNT Libraries Government Documents Department

Impedance Calculations of Non-Axisymmetric Transitions Using the Optical Approximation

Description: In a companion report, we have derived a method for finding the impedance at high frequencies of vacuum chamber transitions that are short compared to the catch-up distance, in a frequency regime that--in analogy to geometric optics for light--we call the optical regime. In this report we apply the method to various non-axisymmetric geometries such as irises/short collimators in a beam pipe, step-in transitions, step-out transitions, and more complicated transitions of practical importance. Most of our results are analytical, with a few given in terms of a simple one dimensional integral. Our results are compared to wakefield simulations with the time-domain, finite-difference program ECHO, and excellent agreement is found.
Date: March 6, 2007
Creator: Bane, K.L.F.; Stupakov, G.; /SLAC; Zagorodov, I. & /DESY
Partner: UNT Libraries Government Documents Department

Measurements of the Transverse Wakefields Due to Varying Collimator Characteristics

Description: We report on measurements of the transverse wakefields induced by collimators of differing characteristics. An apparatus allowing the insertion of different collimator jaws into the path of a beam was installed in End Station A (ESA) in SLAC. Eight comparable collimator geometries were designed, including one that would allow easy comparison with previous results, and were installed in this apparatus. Measurements of the beam kick due to the collimator wakefields were made with a beam energy of 28.5 GeV, and beam dimensions of 100 microns vertically and a range of 0.5 to 1.5 mm longitudinally. The trajectory of the beam upstream and downstream of the collimator test apparatus was determined from the outputs of ten BPMs (four upstream and six downstream), thus allowing a measurement of the angular kick imparted to the beam by the collimator under test. The transverse wakefield was inferred from the measured kick. The different aperture designs, data collection and analysis, and initial comparison to theoretical and analytic predictions are presented here.
Date: July 6, 2007
Creator: Molloy, S.; Seletskiy, Sergei; Woods, Mike; /SLAC; Smith, Jonathan David Andrew; Tech., /Cockcroft Inst. Accel. Sci. et al.
Partner: UNT Libraries Government Documents Department