55319507
CONTROL AND ANALYSIS SYSTEM FOR DIGITAL FEEDBACK IN HLS
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. INTRODUCION 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. CONTROL SYSTEM DESCRIPTION The structural diagram of digital feedback system is shown in Fig. 1 Figure 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 in Fig. 2 Figure 2: 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) # mengming@mail.ustc.edu.cn . MOPE031 Proceedings of IPAC’10, Kyoto, Japan 1038 06 Beam Instrumentation and Feedback T03 Beam Diagnostics and Instrumentation Figure 3: 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. DATA ANALYSING 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
208346202
THE ADJUSTING AND MECHANISM OF THE HCE FOR THE COMMISSIONING OF NSRL
It is discovered that the accumulated current in injection can be raised easily from 200mA to 300mA with the increase of the storage current in the ring, as long as the current of the septum is increased constantly in small quantities, during the commissioning of National Synchrotron Radiation Lab.(NSRL). A tentative exploration is also conducted concerning the mechanism of this high current effect(HCE).
125850686
Transverse Feedback System and Instability Analysis at HLS
In this paper, the BxB transverse feedback systems at Hefei Light Source (HLS) are introduced, which employ an analog system and a digital system. The experiment result of two systems. as well as the primary analysis of beam instability in HLS operation is also presented in this paper. INTRODUCTION HLS is a synchrotron light source,injecting in the energy of 200MeV and operating in the 800MeV. The multi-cycle multi-turn injection system is used for current accumulation. The range of horizontal tune of HLS is from 3.54 to 3.56, and the range of vertical tune is from 2.58 to 2.60 for user operation. The injecting beam current usually cannot exceed 120mA without octupole magnet, and the injecting accumulating beam current is about 250mA with octupole magnet because the beam often occur sudden lose due to CB instabilities in storage ring to limit injection further increase. Therefore the constructing beam feedback system began from 2006 year. The analog feedback system has been built and commissioned at 2007[1-3], At the same time, the development of digital transverse BxB feedback system began at 2007 and has commissioned since 2008[4]. THE ANALOG TFB SYSTEM AND EXPERIMENT RESULTS The diagram of analog TFB system is shown as Figure 1. The analog feedback system is made up of: 3tap filter at centre frequency 612MHz (3*fRF) , hybrid for obtaining beam position oscillation signal, vector algorithm for two BPMs to obtain feedback signal of independent adjustable gain, multiple frequency circuit for centre frequency 612MHz (3*fRF) and 1.2GHz (6*fRF), PXI digitizer for data acquisition modular, the fiber correlator filter for eliminate DC and revolution frequencies, the power amplifier and kicker for exciting beam current. Commissioning Results of Analog TFB at HLS During the commissioning, the damping time and betatron sidebands have been measured by Turn-by-Turn (TBT) [5].and bunch-by-bunch (BXB) [6]. measurement system at beam injecting is shown as Figure 1. Figure 1: Overview of HLS analog TFB after update
122705388
Measurement of the Muon Stopping Power in Lead Tungstate
A large sample of cosmic ray events collected by the CMS detector is exploited to measure the specific energy loss of muons in the lead tungstate of the electromagnetic calorimeter. The measurement spans a momentum range from 5 GeV/c to 1 TeV/c. The results are consistent with the expectations over the entire range. The calorimeter energy scale, set with 120 GeV/c electrons, is validated down to the sub-GeV region using energy deposits, of order 100 MeV, associated with low-momentum muons. The muon critical energy in lead tungstate is measured to be 160+5/-6 plus or minus 8 GeV, in agreement with expectations. This is the first experimental determination of muon critical energy.
26938205
Development of digital transverse bunch-by-bunch feedback system of HLS
Hefei light source (HLS) operates at high beam current with many bunches. Multi-bunch instabilities degrade beam quality. An FPGA based digital transverse bunch-by-bunch feedback system was under development in HLS to suppress beam instabilities. The design of the digital feedback system and primary experiment results are presented in this paper. Further improving of the feedback system and investigating of the characteristics of the feedback loop are the future work.
27175391
Microwave Cold-Testing Techniques for the NLC *
The R & D program for the Next Linear Collider Test Accelerator (NLCTA) includes the development of microwave techniques for testing Xband accelerating structures at different stages of design, manufacturing and assembly. During the design phase, short stacks were built and tested to finalize dimensions. Cell by cell measurements were performed on the NLCTA injector cells as a microwave quality control (QC) after manufacturing. The two injector sections were tuned using a moveable plunger and tested using a semiautomated system of bead-pull. Using this perturbation technique, we were able to map the amplitude and phase of the electric field on the axis throughout the assembled structures under traveling-wave conditions. The development of high-gradient X-band accelerator sections for the Next Linear Collider (NLC), requires low power rf testing techniques that ensure the precise and reliable performance of these sections. For this reason, the NLC Test Accelerator (NLCTA) project [1] provides for an R & D program to develop the low-power testing techniques. These characterizing techniques are aimed at supporting different development phases of the accelerator sections; from the design, through manufacturing, and finally testing of the complete accelerator section. In Fig. 1 we summarize the series of tests that can be used through the development phases of an accelerator section. In this paper, we will outline some of the above testing techniques. Results of measurements performed on the two NLCTA injector sections are presented as examples of the implementation of these testing techniques.
124921771
Search for neutral Higgs boson production through the process e+ e- --> Z* H0
Abstract The results of the searches for neutral Higgs boson production in the process e + e − → Z ∗ H 0 are reported, focusing on Higgs boson masses below 70 GeV. The data sample consists of three million hadronic Z 0 decays collected by the L3 experiment at LEP from 1991 through 1994. No signal is found leading to a lower limit on the mass of the Standard Model Higgs boson of 60.2 GeV at 95% C.L. These results are also interpreted in the framework of the General Two Doublet Model and limits on the nonstandard Higgs boson production through the process e + e − → Z ∗ h 0 are set. A lower limit of 66.7 GeV at 95% C.L. is obtained for the case where the Higgs decays into an invisible final state.