54674221
CALCULATION OF COLLECTIVE EFFECTS AND BEAM LIFETIMES FOR THE LBL 1-2 GeV SYNCHROTRON RADIATION SOURCE
In designing a third-generation high brightness synchrotron radiation source, attention must be paid to the various collective effects that can influence beam performance. We report on calculations, performed with the code ZAP, of the bunch length, the transverse emittance and the beam lifetime (from both Touschek and gas scattering) for our l-2 GeV storage ring. In addition, we estimate the growth times for both longitudinal and transverse coupled bunch instabilities. Bunch lengths of about 20 ps should be obtainable and intrabeam scattering emittance growth is small. For a limiting undulator gap of 1 cm and residual gas pressure of 1 nTorr, the beam lifetime is about 5 hours in the single-bunch mode; in the multibunch mode, lifetimes in excess of 6 hours are expected. These results indicate that all performance goals for the facility should be achievable. prototype Light Source vacuum chamber, we expect the broadband impedance contributed by the vacuum chamber itself to be much smaller than 1 Z,, /n 1 = 2Q. based on user requirements, are as follows:1 nominal beam energy of 1.5 GeV with an energy range 0.75-1.9 GeV, average beam current of 400 mA in the multibunch configuration and 7.6 mA for the single bunch option, horizontal rms emittance less than IO-8 m-rad, rms bunch lengths of lo-25 ps and beam lifetime of at least 6 hours. In this paper, we examine the lattice that was selected to meet these requirements in terms of collective effects that can influence machine performance. First, we discuss the various estimated beam-storage-ring coupling impedances. This allows us to calculate the expected bunch lengths obtainable in the ring, limited by single-bunch instabilities. Effects of coupled bunch instabilities (growth rates and frequency shifts) aie then calculated. The dense beam bunches specified for the Light Source make it necessary to estimate the possible growth in beam emittance due to intrabeam scattering (16s). Calculations confirm that this phenomenon is unimportant at high energies. Finally, we estimate the beam lifetime, taking into account the combined effects of Touschek and gas scattering. All of the calculations reported here were performed with the LBL accelerator physics code ZAP.* Coupling Impedances Many elements in the Light Source storage ring will contribute to the beam-storage-ring coupling impedance. The narrow-band, high-Q impedances arise primarily from the rf cavities, through their higher order modes. These can potentially induce coupled bunch coherent modes. The shunt impedances, resonant frequencies and quality factors for the higher modes of the Light Source rf cavity are taken from experimental observations and calculations for the 500 MHz KEK rf cavity with undamped modes.5 The broadband, low-Q impedance arises from the vacuum chamber itself, together with other elements such as diagnostic instruments, bellows, etc., and the equivalent broadband impedance arising from the many rf cavity modes. This latter rf-equivalent broadband impedance is taken to he 0.2512 per rf cell, as obtained by appropriate summing of the higher order modes of the KEK cavity.5 A detailed impedance inventory has clot been performed yet; however, based on preliminary laboratory measurements4 of the
124556579
Motivation and goals of ERL 2005
Various types of ERL sources are introduced, the relevant beam physics and accelerator technology issues noted, innovative areas of development identified and current and future goals of ERL research and development established.
55285360
Optimization of the Parameters of a Storage Ring for a High Power XUV Free Electron Laser
In this paper we describe the operation of an XUV high gain FEL operating within a bypass of an electron storage ring, and discuss the implications on storage ring optimization imposed by FEL requirements. It transpires that, in the parameter regime of interest, collective effects within the beam play an important role. For example, intrabeam scattering dilutes the transverse emittance of the beam and the microwave instability increases the momentum spread. Both phenomena reduce the effectiveness of the FEL. A computer code, ZAP, has been written which, for a given lattice design, takes all such effects into consideration and produces a figure of merit for FEL operation for that machine. We show the results of ZAP for several storage ring designs, all optimized for FEL operation, and present a design example of a facility capable of producing coherent radiation at 400 Å with tens of megawatts of peak power.
55975443
Accelerator physics experiments at Aladdin
DISCLAIMER LBL--19905 DE86 005847 -J or un or _ames my 1epI liability or reaponli- bility for the accuracy com~ '. or usefuloeu or uy information, apparatus product, or r- _ _ _ _ or ~ts tbat Its UJe would not • I i · · eoce herein to any SpccUlC COOImercial oil ID nnse !, Ya!ely owned rishts. Refer- manufa<1urer, or othcr1¥ise does not PI' .~ pr~, or se~ by trade name, trademark, riI Y mendation, or favorinS by the United Go constItute or Imply its endorsement, recom- es veroment or an v agen thereof Th . e VIews a nd optDlODS of authors ex-..... b . d r'~ erelD 0 not necessarily late flee UDlted States Goveroment or any agency thereof. S or re t those of tbe or work IpOIIIOred b Gom-nmcnl Neilllcr Ik United St.tcs r _ _ y u aaency or the United States -- mUea any ......... ty exPRU JJDJc:nt DOl' uy .... .-~ thereof. or t heir cm.......-. . plied, DOl' any This n:port . . . prepm:d U .. _at ne;;::- ACCELERATOR PHYSICS EXPERIMENTS AT ALADDIN* S. Chattopadhyay, K. Cornacchia, A. Jackson, and K.S. Zisman Lawrence Berkeley Laboratory University of California Berkeley, California 94720 July 1985 This work vas partiaUy supported by the Direcloc-. Office of Enct'yllcl wlib ft.M IlJ.S. hH
51748746
Proposal for a one GeV plasma wakefield acceleration experiment at SLAC
Abstract A plasma-based wakefield acceleration experiment E-157 has been approved at SLAC to study acceleration of parts of an SLC bunch by up to 1 GeV/m over a length of 1 m. A single SLC bunch is used to both induce wakefields in the 1 m long plasma and to witness the resulting beam acceleration. The experiment will explore and further develop the techniques that are needed to apply high-gradient plasma wakefield acceleration to large-scale accelerators. The 1 m length of the experiment is about two orders of magnitude larger than for other high gradient plasma wakefield acceleration experiments and the 1 GeV/m accelerating gradient is roughly ten times larger than that achieved with conventional metallic structures. Using existing SLAC facilities, the experiment will study high gradient acceleration at the forefront of advanced accelerator research.
56152176
CEBAF-ER: Extending the Frontier of Energy Recovery at Jefferson Lab
A successful GeV scale energy recovery demonstration with a high ratio of peak-to-injection energies (50:1) was recently carried out on the CEBAF (Continuous Electron Beam Accelerator Facility) recirculating superconducting linear accelerator in an effort to address issues related to beam quality preservation in a large scale energy recovery system. To gain a quantitative understanding of the beam behavior through the machine, an intense effort was made to characterize the 6D phase space during the CEBAF-ER (CEBAF with Energy Recovery) experimental run. A scheme was implemented to measure the transverse emittance of the energy recovered beam prior to being sent to the dump, as well as in the injector and in each arc. The emittance provides a figure of merit in this context inasmuch as it characterizes the extent to which beam quality is preserved during energy recovery. In addition to describing the transverse phase space, the momentum spread was measured in the injector and arcs to characterize the longitudinal phase space. Measurements also included the RF system's response to the energy recovery process. And by using a novel technique employing wire scans in conjunction with PMTs (Photomultiplier Tubes) to accurately measure the beam profile at the dump, we can qualitativelymore » characterize beam preservation through the recirculator. One of the salient conclusions from the experiment is that the energy recovery process does not contribute to the emittance degradation since the emittance of the recirculating pass is consistent with that of the accelerating pass.« less
123064298
Time of flight (TOF) spectrometer for accurate measurement of mass and angular distribution of fission fragments in heavy ion induced fission reactions
Abstract The performance of a dual time of flight (TOF) spectrometer using two 24 cm×10 cm area X – Y position sensitive Multi-Wire Proportional Counters (MWPC) is reported. Good separation of compound nuclear fission channel from elastic, quasi-elastic and non-compound fission channels have been achieved. Time calibration of the spectrometer using a technique, dependent on the detector independence of the mass or kinetic energy distributions gave a three times better mass resolutions compared to the conventional calibration technique using elastically scattered projectiles in a heavy ion induced fission reaction. Detail experimental methods in determining fission fragment mass and angular distribution have been presented and discussed.
14838499
Density evolution in the new modified Chaplygin gas model
In this paper, we have considered a new modified Chaplygin gas (NMCG) model which interpolates between radiation at an early stage and ΛCDM at a late stage. This model is regarded a unification of dark energy and dark matter (with a general form of matter). We have derived the density parameters from the equation of motion for interaction between dark energy and dark matter. Also, we have studied the evolution of various components of the density parameters.
119115271
Acceleration of the Universe in presence of tachyonic field
Abstract
In this letter, we have assumed that the Universe is filled in tachyonic field with potential, which gives the acceleration of the Universe. For certain choice of potential, we have found the exact solutions of the field equations. We have shown the decaying nature of potential. From recently developed statefinder parameters, we have investigated the role of tachyonic field in different stages of the evolution of the Universe.

53492385
Mechanical prototype of tracking chamber in station 2 in dimuon spectrometer of ALICE
To explore the physics of ultra-relativistic heavy-ion collision, a large ion collider experiment (ALICE) [1] is proposed to carry out at large hadron collider (LHC). Forward muon spectrometer (FMS) [2] is included in ALICE to look for the signals of quark gluon plasma (QGP) using dileptonic decay of heavy quarkonia (J=ψ , γ) produced in the collision as a probe. The production of these states will be suppressed in a deconfined medium of QGP which can be estimated from the invariant mass spectrum of dimuonic decay channel. The spectrometer is designed to track down the flight path of the dimuons with the help of five tracking stations from which the opening angle of the pair can be known by reconstruction and extrapolation of their tracks. The momenta of the pairs can be obtained from the deviation of the tracks in a dipole magnetic field. The invariant mass of the pair can be determined from the opening angle and momenta of dimuon pairs. Each of the five tracking stations is equipped with two planes of cathode pad chamber each divided into four quadrants to detect the position of the dimuon passing through them and reconstruct their tracks from their positions. The tracking chambers are designed following the basic feature of a position sensitive multi-wire proportional counter (MWPC) where an anode wire plane is interposed between two cathode planes and a high electric field is maintained near the anode with respect to the cathodes. The chambers are capable of providing X, Y position readout of an event from the charge distribution induced over the cathode planes equipped with pad matrices due to the avalanche produced in the gaseous medium. However, the mechanical design of the large chamber (diameter 2 m) for the second tracking station is a challenging task as it concerns good surface planarity to achieve position resolution better than 100 μm (necessary to meet mass resolution about 100 MeV) as well as minimum usage of material to keep radiation length low (2–3% of X0) in order to minimise the energy loss and scattering of the incident lepton. The calculation was carried out at IPN, Orsay to simulate a full scale quadrant with different design parameters and materials to study its mechanical characteristics [3,4]. In the simulation, various options in material and design aspects were studied to seek an optimum design for the chamber to enhance its mechanical
119248698
A study on the dependence of the dimensionless Brans-Dicke parameter on the scalar field and their time dependence
Abstract.The present paper reports a study on the dimensionless parameter $ \omega$ in Brans-Dicke theory. Based on a particular choice of scale factor a , we have investigated the signature flip of the deceleration parameter q to see whether the transition from decelerated to accelerated expansion of the universe is achievable under this choice of scale factor. Restrictions on the parameters obtained for this choice of scale factor have been subsequently used for discussing the Brans-Dicke parameter for two choices of scalar fields $ \phi$ . Moreover, analytical solutions for the Brans-Dicke parameter without any assumption about the scalar field have been obtained from the modified field equations through the choice of scale factor under consideration. Viable models have been obtained by comparing the results with observations.