49389105
DESIGN OF MAIN RING DIPOLE POWER SUPPLY FOR HIRFL-CSR *
This paper introduces the main circuit topologic, control method and double reference setting system of a dipole power supply which is the pivotal device of the HIRFL-CSR (Heavy Ion Research Facility in LanzhouCooling Storage Ring). The power supply works at the pulse mode, with the peak output power of 3.15MW (3000A, 1045V). To fulfil difficult requirements especially for the tracking error, which is needed less than 300ppm, a special topologic is adopted. The power supply has two parts: SCR rectifier provides the most energy and PWM converter provides correcting current and perfect reaction for tracking current setting. Now the dipole power supply is performing well during the CSR commissioning, with the perfect tracking error, well longtime stability and low ripple current. INTRODUCTION OF THE POWER SUPPLY The power supply is a pivotal device of HIRFL-CSR (Heavy Ion Research Facility in Lanzhou-Cooling Storage Ring), and it is a synchronized one. This synchronized power supply’s output current must track the setting as Fig. 1. Figure 1: Plots of current and ideal voltage. In Fig. 1, the output voltage only happens at the ideal state. For heavy iron beam acceleration, the most important requirements on the power supply are listed below: Peak output power 3.15MW (3000A/1045V) Tracking error less than 200ppm Current stability better than 3×10 This power supply works at two modes, one is the DC output mode and the other is Pulse output mode, in most cases the control system’s parameters are different at the two modes. DIPOLE POWER SUPPLY’S SCHEMATIC DIAGRAM To fulfil these stringent requirements as mentioned above, our dipole power supply has two parts: SCR rectifier and switching mode DC converter. Fig. 2 shows the schematic diagram of the power supply. In part one, we use 12 SCRs and connect them into two serial normal 3-phases SCR rectifiers. The transformer’s input comes from 10KV power line, and the second side output voltage is 495V.This part provides the most output power (95%). IGBT is adopted in part two, which consists of 4 DC converters. Each DC converter uses a full-Bridge topologic and be connected in serial mode to supply the high-voltage output capability. As we all know, the traditional SCR rectifier has advantages of high power output ability, high credibility and low-cost. But the SCR rectifier also has disadvantage of slow response in synchronized power supply. For the reason mentioned above, the switching mode converter is used to improve the fast-response ability. The very high switching frequency of IGBT makes it easy to control the power supply’s output with a small tracking error. But the switching mode rectifier is of high-cost. In our power supply, we use the advantages of the two modes. It means that the SCR rectifier provides the most output power and the switching mode rectifier provides the fast-response ability for current tracking. There is a balance between the output powers of the two parts. In this power supply, the switching part can supply maximum current up to 200A, but in most cases this part’s maximum output is less than 200A. The maximum output is controlled by a constant input, which is introduced in the following part of this paper.
110247079
Charge division read-out in a 1.8-m-long wire chamber
This paper reports on the design and the test results of a charge division electronic read-out system for a charged particle proportional wire detector. Electronic calibration and probable error analysis of the system are also discussed. Position resolution for the system has been measured to be 4.8-mm FWHM on a wire of 1.8-m length (0.26%, relative). >
102339817
BUNCH-BY-BUNCH ONLINE DIAGNOSTICS AT HLS
The design goal for the bunch-by-bunch analogue transverse feedback system at the Hefei Light Source (HLS) is to cure the transverse coupled bunch instabilities. The prototype implemented bunch-by-bunch feedback in 2006. Then we changed the circuit and replaced some components by ones of higher performance in order to get better effect. Diagnostic techniques are important tools to determine instabilities and to confirm the performance of the feedback systems. In addition to transverse feedback this system can provide online beam diagnostics and analysis in transverse and longitudinal directions. The diagnostic functions can record the response of every bunch while the feedback system manipulates the beam. The experimental results are presented. INTRODUCTION The HLS is a facility dedicated to synchrotron radiation. Its electron storage ring, with a circumference of 66 meters, operates with 45 bunches in 204.035MHz Radio Frequency (RF), and contains 31 BPMs. Each BPM has a four-button type pick-ups mounted in a skew of 45°. A 200MeV injection beam from linac and transport line ramps to 800MeV and operates at 200300mA in the HLS storage ring. A multi-cycle multi-turn injection system is used for current accumulation. A wiggler is available in the HLS. There are three operating states: injection (200MeV), 800MeV Optics-Normal, and 800MeV Optics-Wiggler. A bunch-by-bunch transverse feedback system has been under commissioning at HLS, and it is introduced in this paper. The transverse prototype implemented bunchby-bunch feedback in 2006. In order to get better effect, then we replaced some components by ones of higher performance, such as the strip line feedback kicker, the optical fibre notch filter. We moved the 3-tap filter in front of the hybrid network and add DC offset in the circuit to gain better signal to noise ratio. In addition to transverse feedback this system can provide online beam diagnostics and analysis in transverse and longitudinal directions. The diagnostic functions can record the response of every bunch while the feedback system manipulates the beam. Some phenomena observed are presented, as well as the feedback experimental results. THE FEEDBACK SYSTEM Prototype The bunch-by-bunch analogue transverse feedback system at HLS consists of 2 signal detectors (pickups), a RF front-end, a signal processing, a frequency doubling circuit, a vectors operation and control module, 2 Notch Filters, 4 RF amplifiers and a kicker. An overview of it is in [1]. We use double balance mixers (DBM) to substitute for the attenuators and phase shifters. This new method can simplify the system. It supports a range of 360 degree phase adjusting the feedback signal by vector computation. The signal can be controlled as either a feedback signal or an exciting signal arbitrarily. In order to test the prototype serial experiments were performed on timing, phasing, and powering of the feedback signal with the old 73cm general kicker. This system also works well in 800MeV operation [1].
123932716
Measurement of the Pseudoscalar Decay Constant f(D(s)) Using D(s)+ ---> tau+ nu, tau+ ---> rho+ anti-nu Decays
Analyzing 600 pb ―1 of e + e ― collisions at 4170 MeV center-of-mass energy with the CLEO-c detector, we measure the branching fraction B(D + s → τ + ν) = (5.52 ± 0.57 ± 0.21)% using the τ + → ρ + ν decay mode. Combining with other CLEO measurements of B(D + s → τ + ν) we determine the pseudoscalar decay constant f Ds = (259.7 ± 7.8 ± 3.4) MeV consistent with the value obtained from our D + s → μ + ν measurement of (257.6 ± 10.3 ± 4.3) MeV. Combining these measurements we find a value of f Ds = (259.0 ± 6.2 ± 3.0) MeV, that differs from the most accurate prediction based on unquenched lattice gauge theory of (241 ± 3) MeV by 2.4 standard deviations. We also present the first measurements of B(D + s → K 0 π + π 0 ) = (1.00 ± 0.18 ± 0.04)%, and B(D + s → π + π 0 π 0 ) (0.65 ± 0.13 ± 0.03)%, and measure a new value for B(D + s → ηρ + ) = (8.9 ± 0.6 ± 0.5)%.
125105616
Determination of the B ---> D* l nu decay width and |V(cb)|
55321102
500 MW X-BAND RF SYSTEM OF A 0.25 GEV ELECTRON LINAC FOR ADVANCED COMPTON SCATTERING SOURCE APPLICATION
A Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering light source is being developed at LLNL in collaboration with SLAC National Accelerator Laboratory. The electron beam for the Compton scattering interaction will be generated by a X-band RF gun and a X-band LINAC at the frequency of 11.424 GHz. High power RF in excess of 500 MW is needed to accelerate the electrons to energy of 250 MeV or greater for the interaction. Two high power klystron amplifiers, each capable of generating 50 MW, 1.5 msec pulses, will be the main high power RF sources for the system. These klystrons will be powered by state of the art solid-state high voltage modulators. A RF pulse compressor, similar to the SLED II pulse compressor, will compress the klystron output pulse with a power gain factor of five. For compactness consideration, we are looking at a folded waveguide setup. This will give us 500 MW at output of the compressor. The compressed pulse will then be distributed to the RF gun and to six traveling wave accelerator sections. Phase and amplitude control are located at the RF gun input and additional control points along the LINAC to allow for parameter control during operation. This high power RF system is being designed and constructed. In this paper, we will present the design, layout, and status of this RF system.
118831162
Absolute luminosity measurements with the LHCb detector at the LHC
Absolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC with a centre-of-mass energy of 7 TeV. In addition to the classic "van der Meer scan" method a novel technique has been developed which makes use of direct imaging of the individual beams using beam-gas and beam-beam interactions. This beam imaging method is made possible by the high resolution of the LHCb vertex detector and the close proximity of the detector to the beams, and allows beam parameters such as positions, angles and widths to be determined. The results of the two methods have comparable precision and are in good agreement. Combining the two methods, an overal precision of 3.5% in the absolute luminosity determination is reached. The techniques used to transport the absolute luminosity calibration to the full data-taking period are presented.