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RESULTS FROM BETATRON PHASE MEASUREMENTS IN RHIC DURING THE SEXTANT TEST.

Description: The Sextant Test of the Relativistic Heavy Ion Collider (RHIC) was an important step towards its completion. One sixth of the two RHIC accelerators was fully commissioned. Gold ion beam was injected and transported through one sextant of one of the two rings. The betatron phase advance per cell was measured by recording differences in the horizontal and vertical positions of the beam at the end of the sextant due to a sequence of correction dipole kicks along the beam line. Measurement results show excellent agreement with predicted values, confirming that production measurements of the integral functions of the quadrupoles were very accurate, and that the polarity of all elements (correction dipoles, quadrupoles, dipoles etc.) was correct.
Date: June 26, 1998
Creator: TRBOJEVIC, D.
Partner: UNT Libraries Government Documents Department

A LATTICE FOR THE 50 GEV MUON COLLIDER RING.

Description: A resent progress report on the lattice design of the 50-50 GeV muon collider is presented. The ring circumference needs to be as small as possible due to the short lifetime of the 50 GeV muons. The background at the detector is affected by the continuous decay of muons into electrons which requires a dipole between the high focusing quadrupoles and the detector. To obtain a luminosity on the order of 1 x 10{sup 33} cm{sup {minus}2} S{sup {minus}1} it is required to have beam intensities on the order of 1 x 10{sup 12} particles per bunch. The rms momentum spread of the beam is equal to 0.12% and the beta functions at the interaction point are equal to 4 cm. The maxima of the betatron functions at these quadrupoles are 1300 m, resulting in large chromaticities which must be corrected by local chromatic correction. Pairs of horizontal and vertical chromatic sextupoles are located at locations where the corresponding betatron functions are 100 m and the values of the horizontal dispersion functions are 3 and 2 m, respectively. They are carefully placed so that most of their nonlinear effects are canceled. The dynamic aperture is larger than 7 times the mean size of the beam for the momentum offsets larger than {minus}6 and +10 sigmas.
Date: June 28, 1998
Creator: TRBOJEVIC,D.
Partner: UNT Libraries Government Documents Department

Is the momentum space optimally used with the FODO lattices?

Description: The available momentum space of a FODO lattice is determined by the maximum value of the dispersion function ({delta}x = D{sub x} {partial_derivative}p/p). In a regular FODO lattice the dispersion function oscillates between its maximum and minimum values, which are always positive. The maximum value of the dispersion function in a FODO cell of a fixed length depends on the cell phase difference. An example of a new lattice, in which the dispersion function is lowered to half its value in the same FODO cell, is presented. ne available momentum space in the new lattice is raised to twice that in the FODO lattice by allowing the dispersion function to oscillate between the same positive and negative values. The maxima of the dispersion function in the new lattice have half the value of those within the regular 900 cells.
Date: July 1, 1993
Creator: Trbojevic, D.; Ng, K.Y. & Lee, S.Y.
Partner: UNT Libraries Government Documents Department

A POSSIBLE SYNCHROTRON LIGHT BEAM PROFILE MONITOR IN RHIC.

Description: This report examines the possibility of observing transverse beam profiles by using synchrotron light emission from the 100 GeV/nucleon heavy-ion gold beam in the Relativistic Heavy Ion Collider (RHIC). Synchrotron radiation experiences a shift towards higher photon energy when the magnetic field at the end of a dipole varies rapidly over a short distance. Synchrotron light signals from high energy (larger than 400 GeV) proton beams have already been routinely used to observe the transverse beam profiles at the SPS in CERN and at the TEVATRON at Fermilab. Because of the modest relativistic factor of the fully stripped stored gold ions in RHIC this ''push'' towards higher critical energy is not large enough to place the synchrotron light within the visible region of the spectrum. The critical wavelength remains within the infrared region. A 77K cooled infrared array detector with 160 elements, made of PbSe (Lead salt) could be used for beam profile detection. It would cover the wavelength range between 1 and 6 microns, with maximum sensitivity at a wavelength of 4.5 microns.
Date: June 26, 1998
Creator: TRBOJEVIC, D.
Partner: UNT Libraries Government Documents Department

MEASUREMENTS OF THE BETATRON FUNCTIONS AND PHASES IN RHIC.

Description: The Relativistic Heavy Ion Collider (RHIC) consists of two rings with six fold symmetry. The six interaction regions (IR)s are connected with twelve FODO cells. RHIC quadrupoles in the interaction regions have independent tuning capability. The betatron functions will be measured by a three methods. First, tunable IR quadrupoles will be adjusted to measure betatron functions at those locations through the change in tune. Second, sinusoidal coherent dipole oscillations will be used to measure the betatron phases and functions (as performed in LEP). Third, a correction dipole kick technique will be used (as at Fermilab). Special attention will be given to the ''betatron squeeze'' procedure by which the two large experiments PHENIX and STAR will achieve minimum betatron functions between 1 and 2 m.
Date: June 26, 1998
Creator: TRBOJEVIC, D.
Partner: UNT Libraries Government Documents Department

A STUDY OF RHIC CRYSTAL COLLIMATION.

Description: The Relativistic Heavy Ion Collider (RHIC) will experience increasing longitudinal and transverse heavy ion emittances, mostly due to intra-beam scattering (IBS). The experiments in RHIC are expected to not only have reduced luminosities due to IBS but also background caused by beam halo. Primary betatron collimators will be used to remove the large amplitude particles. The efficiency of the primary collimator in RHIC strongly depends on the alignment of the jaws which needs to be within about ten micro-radians for the optimum conditions. As proposed by V. Biryukov [1] bent crystals could be used to improve the efficiency of an existing collimation system by installing them upstream of the collimator jaws. Bent crystals have been successfully used in SPS, Protvino and Fermilab for extraction of the beam particles channeled through them. This study examines possible improvements of the primary collimator system for heavy ions at RHIC by use of bent crystals. Bent crystals will reduce the collimator jaws alignment requirement and will increase collimator efficiency thereby reducing detector background.
Date: June 26, 1998
Creator: TRBOJEVIC,D.
Partner: UNT Libraries Government Documents Department

Design of the muon collider isochronous storage ring lattice

Description: The muon collider would ex-tend limitations of the e{sup +} e- colliders and provide new physics potentials with a possible discovery of the heavy Higgs bosons. At the maximum energy of 2 TeV the projected luminosity is of the order of 10{sup 35} cm{sup {minus}2}s{sup {minus}1}. The colliding {mu}{sup +} {mu}{sup {minus}} bunches have to be focused to a very small transverse size of few tenths of {mu}m which is accomplished by the betatron functions at the crossing point of {beta}* = 3mm. This requires the longitudinal space of the same length 3 mm. These very short bunches at 2 TeV could circulate only in a quasi-isochronous storage ring where the momentum compaction is very dose to zero. We report on a design of the muon collider isochronous lattice. The momentum compaction is brought to zero by having the average value of the dispersion function through dipoles equal to zero. This has been accomplished by a combination of the FODO cells together with a low beta insertion. The dispersion function oscillates between negative and positive values.
Date: December 1, 1995
Creator: Trbojevic, D.; Courant, E.D.; Lee, S.Y.; Gallardo, J.; Palmer, B.; Tepikian, S. et al.
Partner: UNT Libraries Government Documents Department

Physics of the AGS-to-RHIC transfer line commissioning

Description: This paper presents beam physics results from the fall 1995 AGS-to- RHIC (ATR) transfer line commissioning run with fully ionized gold nuclei. We first describe beam position monitors and transverse video profile monitors, instrumentation relevant to measurements performed during this commissioning. Measured and corrected beam trajectories demonstrate agreement with design optics to a few percent, including optical transfer functions and beamline dispersion. Digitized 2- dimensional video profile monitors were used to measure beam emittance, and beamline optics and AGS gold ion beam parameters are shown to be comparable to RHIC design requirements.
Date: July 1, 1996
Creator: Satogata, T.; Ahrens, L.; Brennan, M.; Brown, K.; Clifford, T.; Connolly, R. et al.
Partner: UNT Libraries Government Documents Department

A standard FODO lattice with adjustable momentum compaction

Description: An existing lattice made of identical FODO cells can be modified to have adjustable momentum compaction. The modified lattice consists of repeating superperiods of four FODO cells where every two cells have different horizontal phase advance. In existing FODO cell rings an additional quad bus is required for every two consecutive cells. This allows tuning of the momentum compaction or {gamma}{sub t} could be an imaginary number. A drawback of this modification is relatively large values of the dispersion function (two or three times larger than in the regular FODO cell design).
Date: July 1, 1997
Creator: Trbojevic, D. & Courant, E.
Partner: UNT Libraries Government Documents Department

A study of betatron and momentum collimators in RHIC

Description: The Relativistic Heavy Ion Collider (RHIC) has two interaction regions where {beta}* = 1--2m, with large detectors PHENIX and STAR. The transverse and longitudinal emittances are expected to double in size between one to two hours due to intra-beam scattering which may lead to transverse beam loss. Primary betatron collimators are positioned in the ring to allow efficient removal of particles with large betatron amplitudes. The authors have investigated distributions and losses coming from the out-scattered particles from the primary collimators, as well as the best positions for the secondary momentum and betatron collimators.
Date: July 1, 1997
Creator: Trbojevic, D.; Stevens, A.J.; Harrison, M.A.; Dell, F. & Peggs, S.
Partner: UNT Libraries Government Documents Department

A proton driver for the muon collider source with a tunable momentum compaction lattice

Description: The future Muon Collider will have a luminosity of the order of 10{sup 35} cm{sup {minus}2{minus}1} during 1,000 turns when the muons decay. This requires 10{sup 12} muons per bunch. The muon source is a 30 GeV proton driver with 2.5 10{sup 13} protons per pulse. The proton bunch length should be of the order of 1 ns. Short bunches could be created by a tunable momentum compaction lattice which would bring the momentum compaction to zero in a short time. This isochronous conduction would allow bunches to shear and become very short in time. The authors present a lattice where the momentum compaction is a tunable parameter at fixed horizontal and vertical betatron tunes. The values of the maxima of the dispersion function are kept small. They examine two kinds of lattices, with combined function as well as normal dipole and quadrupole magnets.
Date: July 1, 1997
Creator: Trbojevic, D.; Brennan, J.M.; Courant, E.D.; Roser, T.; Peggs, S.; Ng, K.Y. et al.
Partner: UNT Libraries Government Documents Department

Preparing accelerator systems for the RHIC sextant commissioning

Description: The Relativistic Heavy Ion Collider (RHIC) construction is progressing steadily towards completion in 1999 when beams will circulate in both collider rings. One of the major tests of the RHIC project was the commissioning of the first sextant with gold ion beams in early 1997. This is a report on preparation of the RHIC accelerator systems for the first sextant test. It includes beam position monitors, timing, injection correction through the magnetic septum and kickers, current transformers, flags and the ionization beam profile monitors, beam loss monitors, beam and quench permit link system, power supply controls, and the configuration database system. The software and hardware development and coordination of the different systems before commissioning were regularly checked during bi-weekly, and (later) weekly, progress report meetings.
Date: July 1, 1997
Creator: Trbojevic, D.; Pilat, F. & Ahrens, L.
Partner: UNT Libraries Government Documents Department

A lattice for the muon collider demonstration ring in the RHIC tunnel

Description: The future {mu}{sup +}{mu}{sup {minus}} Muon Collider should have a luminosity of the order of 10{sup 35} cm{sup {minus}2} s{sup {minus}1}, and the energy of 2 x 2 TeV. The authors present here a demonstration machine at a lower energy to test the feasibility of all components involved, which could be placed inside the existing Relativistic Heavy Ion Collider (RHIC) tunnel. The maximum energy of the muons in the RHIC tunnel depends on the maximum attainable field in the dipoles. The maximum energy in the existing RHIC rings for protons is 250 GeV, where the strength of the magnetic field in the dipoles is 3.5 T. A design of the storage ring lattice for a 50 GeV muon demonstration machine is also presented.
Date: July 1, 1997
Creator: Trbojevic, D.; Palmer, R.B.; Courant, E.D.; Gallardo, J.; Peggs, S.; Tepikian, S. et al.
Partner: UNT Libraries Government Documents Department

Alignment of the high beta magnets in the RHIC interaction regions

Description: The betatron functions inside the triplet quadrupoles in the Relativistic Heavy Ion Collider-RHIC are of the order of 1,500 m, necessitating additional attention in the alignment procedure. On each side of the interaction regions eight cryogenic elements (six quadrupoles and two horizontal bending dipoles) are placed inside large cryostats. The quadrupole magnetic centers are obtained by antenna measurements with an accuracy of {+-} 60 {micro}m. The signals from the antenna were cross calibrated with the colloidal cell measurements of the same magnet. The positions of the fiducials are related to the magnet centers during the antenna measurements. Elements are positioned warm inside the cryostats, with offsets to account for shrinkage during the cool down. The supports at the middle of the two central quadrupoles are fixed, while every other element slides longitudinally inside the cryostat during cool down or warm up.
Date: July 1, 1997
Creator: Trbojevic, D.; Jain, A.; Tepikian, S.; Grandinetti, R.; Ganetis, G.; Wei, J. et al.
Partner: UNT Libraries Government Documents Department

Field quality evaluation of the superconducting magnets of the relativistic heavy ion collider

Description: In this paper, the authors first present the procedure established to evaluate the field quality, quench performance, and alignment of the superconducting magnets manufactured for the Relativistic Heavy Ion Collider (RHIC), and then discuss the strategies used to improve the field quality and to minimize undesirable effects by sorting the magnets. The field quality of the various RHIC magnets is briefly summarized.
Date: May 1, 1995
Creator: Wei, J.; Gupta, R.C.; Jain, A.; Peggs, S.G.; Trahern, C.G.; Trbojevic, D. et al.
Partner: UNT Libraries Government Documents Department

A possible synchrotron light beam profile monitor in RHIC

Description: This report examines the possibility of observing transverse beam profiles by using synchrotron light emission from the 100 GeV/nucleon heavy-ion gold beam in the Relativistic Heavy Ion Collider (RHIC). Synchrotron radiation experiences a shift towards higher photon energy when the magnetic field at the end of a dipole varies rapidly over a short distance. Synchrotron light signals from high energy (larger than 400 GeV) proton beams have already been routinely used to observe the transverse beam profiles at the SPS in CERN and at the TEVATRON at Fermilab. Because of the modest relativistic factor of the fully stripped stored gold ions in RHIC this push towards higher critical energy is not large enough to place the synchrotron light within the visible region of the spectrum. The critical wavelength remains within the infrared region. A 77 K cooled infrared array detector with 160 elements, made of PbSe (Lead Salt) could be used for beam profile detection. It would cover the wavelength range between 1 and 6 microns, with maximum sensitivity at a wavelength of 4.5 microns.
Date: August 1, 1998
Creator: Trbojevic, D.; Courant, E.; Peggs, S. & Hahn, A.
Partner: UNT Libraries Government Documents Department

RHIC injection kicker impedance

Description: The longitudinal impedance of the RHIC injection kicker is measured using the wire method up to a frequency of 3 GHz. The mismatch between the 50 ohm cable and the wire and pipe system is calibrated using the TRL calibration algorithm. Various methods of reducing the impedance, such as coated ceramic pipe and copper strips are investigated.
Date: May 1, 1995
Creator: Mane, V.; Peggs, S.; Trbojevic, D. & Zhang, W.
Partner: UNT Libraries Government Documents Department

A lattice for the 50 GeV muon collider ring

Description: A recent progress report on the lattice design of the 50-50 GeV muon collider is presented. The ring circumference needs to be as small as possible due to the short lifetime of the 50 GeV muons. The background at the detector is affected by the continuous decay of muons into electrons which requires a dipole between the high focusing quadrupoles and the detector. To obtain a luminosity on the order of 1{times}10{sup 33} cm{sup {minus}2} s{sup {minus}1} it is required to have beam intensities on the order of 1{times}10{sup 12} particles per bunch. The rms momentum spread of the beam is equal to 0.12% and the beta functions at the interaction point are equal to 4 cm. The maxima of the betatron functions at these quadrupoles are 1,300 m, resulting in large chromaticities which must be corrected by local chromatic correction. Pairs of horizontal and vertical chromatic sextupoles are located at locations where the corresponding betatron functions are 100 m and the values of the horizontal dispersion functions are 3 and 2 m, respectively. They are carefully placed so that most of their nonlinear effects are canceled. The dynamic aperture is larger than 7 times the mean size of the beam for the momentum offsets larger than {minus}6 and +10 sigmas.
Date: August 1, 1998
Creator: Trbojevic, D.; Ng, K.Y. & Weishi, W.
Partner: UNT Libraries Government Documents Department

RHIC sextant test: Accelerator systems and performance

Description: One sextant of the RHIC Collider was commissioned in early 1997 with beam. We describe here the performance of the accelerator systems, instrumentation subsystems and application software. We also describe a ramping test without beam that took place after the commissioning with beam. Finally, we analyze the implications of accelerator systems performance and their impact on the planning for RHIC installation and commissioning.
Date: August 1, 1997
Creator: Pilat, F.; Trbojevic, D. & Ahrens, L.
Partner: UNT Libraries Government Documents Department

The Lattice for the 50-50 GeV Muon Collider

Description: The lattice design of the 50-50 Gev muon collider is presented. Due to the short lifetime of the 50 GeV muons, the ring needs to be as small as possible. The 4 cm low betas in both planes lead to high betatron functions at the focusing quadrupoles and hence large chromaticities, which must be corrected locally. In order to maintain a low rf voltage of around 10 MV, the momentum-compaction factor must be kept to less than 10{sup -2} , and therefore the flexible momentum-compaction modules are used in the arcs. The dynamical aperture is larger than 6 to 7 rms beam size for {+-}5 rms momentum offset. Comments are given and modifications are suggested.
Date: February 1, 1998
Creator: Ng, K.-Y., Trbojevic, D.
Partner: UNT Libraries Government Documents Department

The effect and correction of coupling generated by the RHIC triplet quadrupoles

Description: This study explores the possibility of operating the nominal RHIC coupling correction system in local decoupling mode, where a subset of skew quadrupoles are independently set by minimizing the coupling as locally measured by beam position monitors. The goal is to establish a correction procedure for the skew quadrupole errors in the interaction region triplets that does not rely on a priori knowledge of the individual errors. After a description of the present coupling correction scheme envisioned for RHIC, the basics of the local decoupling method will be briefly recalled in the context of its implementation in the TEAPOT simulation code as well as operationally. The method is then applied to the RHIC lattice: a series of simple tests establish that single triplet skew quadrupole errors can be corrected by local decoupling. More realistic correction schemes are then studied in order to correct distributed sources of skew quadrupole errors: the machine can be decoupled either by pure local decoupling or by a combination of global (minimum tune separation) and local decoupling. The different correction schemes are successively validated and evaluated by standard RHIC simulation runs with the complete set of errors and corrections. The different solutions and results are finally discussed together with their implications for the hardware.
Date: May 1, 1995
Creator: Pilat, F.; Peggs, S.; Tepikian, S.; Trbojevic, D. & Wei, J.
Partner: UNT Libraries Government Documents Department

A study of betatron and momentum collimators in RHIC

Description: Two separate accelerator rings in the Relativistic Heavy Ion Collider (RHIC) will provide collisions between equal and unequal heavy ion species up to the gold ions, including the two polarized proton beams. There are six interaction points with two regions with {beta}* = 1--2 m occupied by the large detectors PHENIX and STAR. The transverse and longitudinal emittances of the gold ions are expected to double in size between one to two hours due to intra-beam scattering which may lead to transverse beam loss. Primary betatron collimators are positioned in the ring where the betatron functions have large values to allow efficient removal of particles with large betatron amplitudes. In this report the authors investigated distributions and losses coming from the out-scattered particles from the primary collimators, as well as the best positions for the secondary momentum and betatron collimators. Additional studies of the detector background due to beam halo and other details about the collimation in RHIC are reported elsewhere, while more information about the momentum collimation was previously reported in Momentum Collimation at Q9 by S. Peggs and G.F. Dell.
Date: December 1, 1997
Creator: Trbojevic, D.; Stevens, A.J. & Harrison, M.
Partner: UNT Libraries Government Documents Department

Measurements of the betatron functions and phases in RHIC

Description: The Relativistic Heavy Ion Collider (RHIC) consists of two rings with six fold symmetry. The six interaction regions (IR)s are connected with twelve FODO cells. RHIC quadrupoles in the interaction regions have independent tuning capability. The betatron functions will be measured by a three methods. First, tunable IR quadrupoles will be adjusted to measure betatron functions at those locations through the change in tune. Second, sinusoidal coherent dipole oscillations will be used to measure the betatron phases and functions (as performed in LEP). Third, a correction dipole kick technique will be used (as at Fermilab). special attention will be given to the betatron squeeze procedure by which the two large experiments PHENIX and STAR will achieve minimum betatron functions between 1 and 2 m.
Date: August 1, 1998
Creator: Trbojevic, D.; Kewisch, J.; Peggs, S.; Satogata, T.; Tepikian, S. & Goddere, G.
Partner: UNT Libraries Government Documents Department