121844494
FEL potential of eRHIC
Brookhaven National Laboratory plans to build a 5-to-30 GeV energy-recovery linac (ERL) for its future electron-ion collider, eRHIC. In past few months, the Laboratory turned its attention to the potential of this unique machine for free electron lasers (FELS), which we initially assessed earlier. In this paper, we present our current vision of a possible FEL farm, and of narrow-band FEL-oscillators driven by this accelerator. eRHIC, the proposed electron-ion collider at BNL, takes advantage of the existing Relativistic Heavy Ion Collider (RHIC) complex. Plans call for adding a six-pass super-conducting (SRF) ERL to this complex to collide polarized- and unpolarized- electron beams with heavy ions (with energies up to 130 GeV per nucleon) and with polarized protons (with energies up to 325 GeV). RHIC, with a circumference of 3.834 km, has three-fold symmetry and six straight sections each {approx} 250 m long. Two of these straight sections will accommodate 703-MHz SRF linacs. The maximum energy of the electron beam in eRHIC will be reached in stages, from 5 GeV to 30 GeV, by increasing the lengths of its SRF linacs. We plan to install at the start the six-pass magnetic system with small gap magnets. The structure of the eRHIC'smore » electron beam will be identical with that of its hadron beam, viz., 166 bunches will be filled, reserving about a one-microsecond gap for the abort kicker. With modest modifications, we can assure that eRHIC's ERL will become an excellent driver for continuous wave (CW) FELs (see Fig.1). The eRHIC's beam structure will support the operation of several such FELs in parasitic mode.« less
23683095
Study of electron-proton beam-beam interaction in eRHIC
Beam-beam effects present one of major factors limiting the luminosity of colliders. In the linac-ring option of eRHIC design, an electron beam accelerated in a superconducting energy recovery linac collides with a proton beam circulating in the RHIC ring. There are some features of beam-beam effects, which require careful examination in linac-ring configuration. First, the beam- beam interaction can induce specific head-tail type instability of the proton beam referred to as 'kink' instability. Thus, beam stability conditions should be established to avoid proton beam loss. Also, the electron beam transverse disruption by collisions has to be evaluated to ensure beam quality is good enough for the energy recovery pass. In addition, fluctuations of electron beam current and/or electron beam size, as well as transverse offset, can cause proton beam emittance growth. The tolerances for those factors should be determined and possible countermeasures should be developed to mitigate the emittance growth. In this paper, a soft Gaussian strong-strong simulation is used to study all of mentioned beam-beam interaction features and possible techniques to reduce the emittance growth.
73528019
Emittance and Bunch Length Measurement of the Electron Beams from the NSRRC Photocathode Gun
A high brightness photo-injector is under development for single pass FEL research at NSRRC. The gun test facility (GTF) equipped with a photocathode rf gun a compensation solenoid, a S-band high power pulse klystron as well as a UV driver laser has been constructed for testing the photocathode rf gun. The gun is fabricated in house and being tested at the GTF. Since the transverse emittance is a key property of the electron beam from the rf gun, multi-slit method is used to characterize the transverse emittance of the electron beam. Another key property of the electron beam is bunch length. An S-band three-cell deflecting cavity is designed to measure the bunch length. The setup and results of emittance measurement as well as the structure design of the deflecting cavity is reported in this contribution.
55740595
Present Status of Coherent Electron Cooling Proof-of-Principle Experiment
The status of FEL-based Coherent Electron Cooling Proof-of-principle Experiment at BNL is presented. The experimental set-up is comprised of a 2 MeV CW SRF electron gun and 20 MeV CW SRF linac and 8-m long helical FEL amplifier. The status of the accelerator commissioning, and progress in the construction of the helical undulator at Budker INP, is also reported.
95559577
Gold Nanoclusters Entrapped in the α-Cages of Y Zeolites: Structural Characterization by X-ray Absorption Spectroscopy
Au(CH3)2(C5H7O2) was used as a precursor to synthesize mononuclear gold complexes in faujasites, NaY zeolite, and dealuminated Y zeolite. Treatment of these supported complexes in flowing helium as the temperature was increased led to the gradual reduction of the gold and formation of gold nanoclusters in each zeolite, which were characterized by X-ray absorption spectroscopy. After treatment at the highest temperature, 573 K, the average diameters of the gold clusters were approximately 10 and 8 A in NaY zeolite and dealuminated Y zeolite, respectively; these clusters are smaller than the diameters of the α-cages of the zeolite. The results indicate that the supported clusters were trapped within these cages and that the cages limited their sizes; in contrast, clusters formed similarly on the surfaces of metal oxides are significantly larger than those formed in the zeolites.
56296740
RHIC performance for fy2012 heavy ion run
In the 2012 RHIC heavy ion run, we collided uraniumuranium (U-U) ions at 96.4 GeV/nucleon and copper-gold (Cu-Au) ions at 100 GeV/nucleon for the first time in RHIC. The new Electron-Beam Ion Source (EBIS) was used for the first time to provide ions for the RHIC physics program. After adding the horizontal cooling, 3-D stochastic cooling became operational in RHIC for the first time, which greatly enhanced the luminosity. With a double bunch merging technique in the Booster and AGS, the bunch intensities of Cu and Au ions in RHIC surpassed their projections. Both PHENIX and STAR detectors reached their integrated luminosity goals for both U-U and Cu-Au collisions. In this article we review the machine improvements and performances in this run.
107782453
Reducing the Impedance of the Flange Gaps in BEPC Vacuum Chamber
122993825
Field measurement of PEP-II LER dipoles and quadrupoles at IHEP
The field measurement of 209 dipoles and 320 quadrupoles for PEP-II LER will be finished at IHEP in June 1997. This paper covers the details of the magnetic measurement devices developed to measure these magnets as well as the results of the measurements.
110035692
DESIGN OF LOW IMPEDANCE ELECTROSTATIC SEPARATORS FOR BEPC II
The multi bunch train collision is adopted in BEPC II. There are 4 horizontal electrostatic separators in the main ring to generate close-orbit displacement as "pretzels" which allow the electrons and positrons to be stored in the same vacuum chamber simultaneously without unwanted destructive collisions. In the separator the beam current (576mA) and the gap voltage (220 kV) are both very high. So there are five key problems that must be handled well: To reduce the beam impedance and loss factor; To absorb the high order modes (HOMs); To reduce the leakage of RF EM field; To extract the heats due to the HOMs losses and the SR power; To reduce the spark rate. Their analysis and the solutions are presented in this paper.
110270067
PRELIMINARY DESIGN OF FAST KICKER SYSTEM FOR BEPC II
With in BEPC II injection system there are two sets injection lines in storage ring each consisting of a pair of kicker magnets and one Lambertson magnet for e + and e injection respectively. The incoming beam is injected horizontally inside the storage ring. The linac provides the short pulsed bunch train of 3 micro bunches. There are six e + and six e -- bunch trains countermove in a same ring. The single bunch train injection is chosen. The duration of bunch train is 16ns. The kick of field is 130 Gauss-meter. The type of lumped ferrite inductance magnet with ceramic vacuum chamber is chosen. Per magnet consists of four modules each of 30 cm long, The field strength of magnet is 108 gauss. Excitation current is 631 A .The pulse field of magnet is a trapezoidal wave with duration less than 110ns, rise / fall time of K1 and fall / rise time of K2 is 33ns / 50ns respectively. The lumped LC network with impedance of 30ohm and voltage of 38kV is chosen as a pulser. The stray inductance of lead is controlled to be small enough by an air-insulated coaxial construction. Field rise time is reduced by the compensating capacitance and the fall time is reduced by second switch and saturable reactor. A ZVS PWM type of high voltage power supply is chosen as the charger for PFN. The details are described in this paper.