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.  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 . 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 .

title: A Close Binary Star Resolved from Occultation by 87 Sylvia
abstract: The star BD +29 1748 was resolved to be a close binary from its occultation by the asteroid 87 Sylvia on 2006 December 18 UT. Four telescopes were used to observe this event at two sites separated by some 80 km. Two flux drops were observed at one site, whereas only one flux drop was detected at the other. From the long-term variation of Sylvia, we inferred the probable shape of the shadow during the occultation, and this in turn constrains the binary parameters: the two components of BD +29 1748 have a projected separation of 0:097-0:140 on the sky with a position angle 104°-110°. The asteroid was clearly resolved, with a size scale ranging from 130 to 290 km as projected onto the occultation direction, consistent with the size dimensions 385 × 265 × 230 km, mea- sured by direct adaptive optics imaging. No occultation was detected for either of the two known moonlets of 87 Sylvia.

title: HLS Turn-by-Turn System and its Application
abstract: Measurement principles and analysis of Turn-by-Turn beam position monitor system at Hefei Light Source (HLS) are presented in this paper. In emphases, several typical applications are presented here, which include the commissioning of upgraded injection system on HLS storage, monitoring of transientν transientν transientν transientν transientν transientν transientν transientν transientν transientν and damping time of storage ring, beam instability in injection, as well as experiments of low frequency feedback system. Precise analyses of experimental results offer some conclusions, which are consistent with theoretical expectations. The system plays an important role in study of beam instability and improvement of machine performance.

title: Bunch Tracing by Bunch by Bunch Measurement System in HLS
abstract: In this paper, we introduce a bunch tracing system which is based on a bunch-by-bunch (BxB) measurement system in Hefei Light Source (HLS), and present the analysis of the experiment results. Using an in-phase gate signal and a double balance mixer to control an external trigger of ADC, we test the reliability of the BxB system. By this system, we can trace all marked bunches in a set time slot or in manual burst mode. We can record all bunches’ data during the injection, ramping, wiggler excitation and normal operation, and provide a powerful facility for machine study.

title: GRB 071112C: A Case Study of Different Mechanisms in X-ray and Optical Temporal Evolution
abstract: We present a study on GRB 071112C X-ray and optical light curves. In these two wavelength ranges, we have found different temporal properties. The R-band light curve showed an initial rise followed by a single power-law decay, while the X-ray light curve was described by a single power-law decay plus a flare-like feature. Our analysis shows that the observed temporal evolution cannot be described by the external shock model in which the X-ray and optical emission are produced by the same emission mechanism. No significant color changes in multi-band light curves and a reasonable value of the initial Lorentz factor ({Gamma}{sub 0} = 275 {+-} 20) in a uniform interstellar medium support the afterglow onset scenario as the correct interpretation for the early R band rise. The result suggests that the optical flux is dominated by afterglow. Our further investigations show that the X-ray flux could be created by an additional feature related to energy injection and X-ray afterglow. Different theoretical interpretations indicate the additional feature in X-ray can be explained by either late internal dissipation or local inverse-Compton scattering in the external shock.

title: Electromagnetic calorimeter with thin gap wire chambers
abstract: In this paper we report about the experimental results obtained in a beam test of a gas sampling EM calorimeter. The module consists of 20 thin gap (30 mm) multiwire chambers as active elements, interleaved with brass absorber plates of 12 mm thickness or 0.84 radiation length. The KEK electron beam was tuned to energies of 0.5, 1.0, 2.0, 3.0, 4.0 GeV. The construction and performances of the chamber, the assembling of the module, the experimental setup and data acquisition system are briefly described. The energy resolution of the module is found to be 25%√E (E in GeV). In the range of measured energies, good linearity of the energy response is obtained. The longitudinal development of EM shower, the relation between energy resolution and thickness of the absorber as well as the high voltage of the chamber are studied. The effect of incident position of the beam on the performance of the module is also given.

title: Testing and Data Reduction of the Chinese Small Telescope Array (CSTAR ) for Dome A, Antarctica
abstract: The Chinese Small Telescope Array (CSTAR) is the first Chinese astronomical instrument on the Antarctic ice cap. The low temperature and low pressure testing of the data acquisition system was carried out in a laboratory refrigerator and on the 4500 m Pamirs high plateau, respectively. The results from the final four nights of test observations demonstrated that CSTAR was ready for operation at Dome A, Antarctica. In this paper, we present a description of CSTAR and the performance derived from the test observations.

title: Search for microscopic black holes in pp collisions at $ \sqrt{s}=8 $ TeV
abstract: A bstractA search for microscopic black holes and string balls is presented, based on a data sample of pp collisions at $ \sqrt{s}=8 $ TeV recorded by the CMS experiment at the Large Hadron Collider and corresponding to an integrated luminosity of 12 fb−1. No excess of events with energetic multiparticle final states, typical of black hole production or of similar new physics processes, is observed. Given the agreement of the observations with the expected standard model background, which is dominated by QCD multijet production, 95% confidence level limits are set on the production of semiclassical or quantum black holes, or of string balls, corresponding to the exclusions of masses below 4.3 to 6.2 TeV, depending on model assumptions. In addition, model-independent limits are set on new physics processes resulting in energetic multiparticle final states.

title: CONTROL AND ANALYSIS SYSTEM FOR DIGITAL FEEDBACK IN HLS
abstract: In HLS we employ the TED FPGA based processor for digital feedback system. To make feedback system work better and more easily, we developed the control and analysis system based on Matlab chiefly. The system do jobs as following: sampling data online and finishing its analysis; calculating FIR filter parameters and generating .CSV (format for FPGA) file to get the best gain and phase flexibly according to different beam working point; simulating the beam changes in different feedback gain and other stations to check whether the system work properly.  HLS uses the octopole magnet to help injection at the present time, but octopole magnet will cause nonlinearity and change the dynamic aperture, after the update plan of HLS finished, octopole magnet cannot be used anymore, then the feedback system should be used to suppress beam instabilities and improve injection efficiency. Compared to analog feedback system, digital feedback system is more simple and flexible, also it’s more reliable because of less affected by transport noise. We can use the fir filter in processor to get more feedback effect. So developing a control system fitting digital feedback for doing some analyzing is very useful for taking full advantage of digital feedback.  The structural diagram of digital feedback system is shown in Fig. 1  Structure block of digital feedback. After the beam signal is processed by RF front-end, it is sampled by 6 ADC in the feedback processor .The FPGA inside handles data and outputs it to kicker through DAC. During the process, command and data is transported in/out by USB2.0 interface when we need to change the system. In the processor made by TED the USB chip used is CY7C68 series, it’s the first micro processor controller interface chip with USB2.0 protocol inside in the world. The max transform speed can be 480 Mbps. The interface is Hot Swap so that it can protect the instrument and the control can be very flexible too. In the past the control soft we use is presented with machine. It is a command line programme and only contains some basic functions so that using of it is also very inconvenient while we need to debug the feedback machine; On the other hand the updated data which sampled by ADC is too much to analyze online, while sometimes we need to know some parameters of beam online, so we can develop an new control system to change the situation. To decrease the amounts of work as far as possible we take use of DLL part of the programme used before after reprogramming it. DLL (Dynamic Link Library) packages some executable codes and data in it while supplying us with calling in/out interface. The existed DLL is already compiled with C language based on driver of CY7C68 chip, so using it we don’t have to write driver again, that is not so easy. In our work we rewrite sublayer communication functions; they call basic I/O functions to control the system by CY7C68. The control system is carried out with Matlab. Matlab has a big advantage on data analyzing. In new edition Matlab such as 2008, support of calling function in DLL is more perfect. The contrast of data type used in C and MATLAB is  Data type compared in c and Matlab. To make the structure of control system simple, we put most of the operation in DLL, so when using Matlab soft we just have to know the name of functions in DLL and what parameter we should pass to it. The soft uses MATLAB GUI (Graphical user interface) to make users easily operate it. Fig. 3 shows the panel of control GUI _________________________________________ *Work supported by National Natural Science Project (10175063)  Beam Diagnostics and Instrumentation  Control system with Matlab. Its working chain is as follows: calling loadlibrary function to load DLL, calling calllib function to use functions in DLL, among which registerwrite, registerread function is for register reading and writing, adcmemoryupload function is for ADC data operating. First we should call deviceopen function to open device and establish connect; for DAC, address 0x8022 determines its on/off state. 0x8008,0x802A,0x800A,0x802C,0x800C are the output delay of DAC0-4 the last three bits of 0x8020 determine inverting state of 3 DAC 0x8012,0x8014 are the gain of DAC, 0x8004 0x801A determine the fir filter parameters; For ADC, 0x805C assigns the uploadsize of updating data, of which minimum value is 128K, 0x8058 are in charge of updating by writing 2,1,4 to it in queue, 0x805a shows the change of ADC station while translating data. Following the steps, we finish the control system.  With the data sampled by control system, we can do some analyse to get some important parameters of beam. Fir Coefficient In the processor, we use FIR filter in FPGA, the filter can separate unwanted DC constituent and other noise at cyclotron frequency, avoiding the saturation of ADC. It also has to exert right phase and gain on signal. FIR can be carried out easily when hundreds of Mb data should be processed in some ns time. In the FPGA, we employ least square method to design FIR filter . FIR can be expressed as

title: SPEAR3 BOOSTER RF SYSTEM UPGRADE: PERFORMANCE REQUIREMENTS AND EVALUATION OF RESOURCES *
abstract: The SPEAR2 accelerator system originally had 3 RF stations (2 for storage ring, 1 Booster) operating at 358.5 MHz. SPEAR3 now operates at 476.3 MHz with the PEPII type RF system, while the Booster RF frequency remains unchanged. For top-off operation, the Booster injects single 3.0 GeV electron bunches into SPEAR3 at 10 Hz every 5 minutes to replenish lost charge. Due to the frequency mismatch between SPEAR3 and the Booster, only one SPEAR3 bucket can injected per shot limiting injection rate and overall system flexibility. The aging high-power RF subsystems of the Booster pose a reliability issue as well. In order to remove these constraints, studies are underway to replace the Booster RF system using the PEP-II type RF system as a baseline. The new Booster RF system will be tuned to 475.036 MHz, and phase-locked to the SPEAR3 RF system. The project calls for ramping the Booster cavity gap voltage to 0.80 MV at 10 Hz, each with a 40 ms acceleration interval. With very low beam loading and low average RF power, there are many subsystems that can be operationally simplified. In this paper we present the results of analysis leading to a new Booster RF system.

title: Observation of chicJ radiative decays to light vector mesons.
abstract: Using a total of 2.74 x 10(7) decays of the psi(2S) collected with the CLEO-c detector, we present a study of chi(cJ)-->gammaV, where V=rho(0), omega, phi. The transitions chi(c1)-->gammarho(0 and chi(c1)-->gammaomega are observed with B(chi(c1)-->gammarho(0))=(2.43+/-0.19+/-0.22) x 10(-4) and B(chi(c1)-->gammaomega)=(8.3+/-1.5+/-1.2) x 10(-5). In the chi(c1)-->gammarho(0) transition, the final state meson is dominantly longitudinally polarized. Upper limits on the branching fractions of other chi(cJ) states to light vector mesons are presented.