摘要:

Ten fluorescent screens and cameras determine the relative position and image profile of the beam in both the electron and positron linacs at the Advanced Photon Source (APS). The timing techniques used to capture the beam image allow direct synchronization to the electron gun trigger to minimize timing uncertainties. This paper will discuss the design and status of the APS linac fluorescent screen assemblies and imaging system.

ISSN:0094-243X    

DOI:10.1063/1.46982

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A brief overview of the rf system is given. Design and operating parameters for the klystron amplifiers powering the single cell cavities are described with operating parameters for various positron beam intensities and for optimization of the feedback loops. Klystron efficiencies are low except in saturated operation, but any feedback loop around the klystron requires at least some klystron gain. The gain in the amplitude feedback loop must be adjusted to compensate for saturation. The operating point of the klystron may be dynamically adjusted through a pre‐programmed computer or dedicated local processor. Feed forward techniques may be used to alter the program based on beam intensity over the ten‐hour storage cycle, using a new digitizer module from Hewlett‐Packard. Reduction of the cavity impedance for multi‐bunch operation is also described.

ISSN:0094-243X    

DOI:10.1063/1.46983

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A description of the SSCL RFQ‐DTL Matching Section instrumentation is presented with emphasis on design issues and early instrumentation commissioning results. The H−beam energy through the RFQ‐DTL matching section is 2.5 Mev, the beam current is 27 mA with a pulse width of 35 &mgr;s. The typical beam diameter is 3 mm. The instrumentation consists of three beam position monitors (BPM), a wire scanner, beam loss monitors (BLM), a slit and collector emittance measurement unit (EMU), a current toroid, and a Faraday cup. The instruments were designed to accommodate high current densities, have a large dynamic range with moderate bandwidths, and fit congested spaces.

ISSN:0094-243X    

DOI:10.1063/1.46957

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

During the past two years, the Ground Test Accelerator (GTA) has used a variety of off‐ and on‐line beam diagnostic measurements to understand and verify the transverse and longitudinal phase space characteristics of a 35‐mA, low‐energy (2.5‐ to 3.2‐MeV) H−‐beam. For the transverse phase‐space characterization measurements, a slit and collector device samples of thex−x’andy−y’phase space, to determine the transverse emittance and Courant–Snyder parameters. The longitudinal phase‐space data are acquired by a laser neutralization technique developed at Los Alamos know as the laser induced neutralization diagnostics approach (LINDA). The transverse and longitudinal phase‐space centroids of the low‐energy, 425‐MHz‐bunched beam are directly measured using the microstrip probe systems. Beam current and transmission are measured by various toroid systems. Beam‐loss‐detection techniques have just been installed and a non‐interceptive beam‐profile measurement has been commissioned. All of these measurement systems have had their share of successes and challenges. For example, while the microstrip‐system’s energy, phase, and intensity measurements operated successfully, their beam‐position‐measurement calibrations did not agree with either wire calibration data or measured slit‐and‐collector beam‐centroid data due to perturbations to the beam’s image‐current distributions and low‐&bgr; effects of the probe’s position‐detection sensitivity. This paper describes the measurement systems and commissioning team’s experiences using these systems.

ISSN:0094-243X    

DOI:10.1063/1.46958

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Multi‐bunch transfer functions are principal ingredients in understanding both the behavior of high‐current storage rings as well as control of their instabilities. The measurement of transfer functions on a bunch‐by‐bunch basis is particularly important in the design of the active feedback systems. Traditional methods of network analysis that work well in the single bunch case become difficult to implement for many bunches. We have developed a method for obtaining empirical estimates of the multi‐bunch longitudinal transfer functions from the time‐domain measurements of the bunches’ phase oscillations. This method involves recording the response of the bunch of interest to a white‐noise excitation. The transfer function can then be computed as the ratio of the fast Fourier transforms (FFTs) of the response and excitation sequences, averaged over several excitations. The calculation is performed off‐line on bunch‐phase data and is well‐suited to the multi‐bunch case. A description of this method and an analysis of its performance is presented with results obtained using the longitudinal quick prototype feedback system developed at SLAC.

ISSN:0094-243X    

DOI:10.1063/1.46959

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

EG&G/EM has developed an oscilloscope with a −3 dB bandwidth greater than 10 GHz. Its rolloff characteristics are such that single‐transient data greater than 20 GHz may be captured. A demountable CCD camera records the oscilloscope trace and is provided with PC‐compatible capture and data processing software. The capabilities of the oscilloscope, camera, and its processing software are described and examples of the system’s performance is shown. This work supported by the U.S. Department of Energy, Nevada Operations Office, under Contract No. DE‐AC08‐93NV11265.

ISSN:0094-243X    

DOI:10.1063/1.46960

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

At full intensity the energy contained in each beam of the Superconducting Super Collider (SSC) is 400 MJ. The loss of a small fraction of that beam has the potential to cause magnet quenches or even severe damage to Collider components. To help protect the machine a sensitive and reliable beam loss monitor (BLM) system must be designed and built. In fact, BLM systems will be needed for all the accelerators of the SSC. The BLM system requirements for each of these accelerators will be discussed, but emphasis will be placed on the Collider. The discussion will include the preliminary design of BLM systems, the considerations that led to these designs, the calculations that were performed in development of the designs, and the problems that remain to be solved. A major tool in the design process has been a series of Monte Carlo calculations that were used to estimate beam loss distributions for the Collider arcs, the interaction regions, and the west utility region. These calculations were also used to study the fluence as a function of energy, the particle content, and the dose rate at selected positions. Detailed considerations such as detector spacing and sensitivity, loss fluctuations, reliability, and maintainability will be discussed. The proposed preliminary BLM system design for the Collider uses a radiation‐hard, solid‐state ionization detector and fast analog‐to‐digital conversion. Details of this design and relevant options will be discussed.

ISSN:0094-243X    

DOI:10.1063/1.46961

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

This paper will present the final tests of the APS storage ring BPM electronic system. The final configuration includes the filter‐comparator installed in the accelerator tunnel and the signal conditioning and digitizing unit (SCDU) in a VXI configuration. The SCDU includes an AM/PM monopulse receiver at 352 MHz. Extensive testing was performed on the system. The key parameters measured were the null cancellation better than 45 db, dynamic range of better than 40 db, single bunch capability with 0.01 mA sensitivity, and a resolution better than 10 micron for 512 averaged turns. This last critical performance was tested using a moving wire to simulate the beam. This report will concentrate on the wire test results. Also, the actual production hardware will be presented.

ISSN:0094-243X    

DOI:10.1063/1.46963

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

One of the research and development thrusts at the Advanced Photon Source (APS) is to use an rf gun as a low‐emittance electron source for injection into the 100‐ to 650‐MeV linac subsystem and subsequent transport to an undulator test area. This configuration would combine the acceleration capability of the 200‐MeV S‐band electron linac and the in‐line 450‐MeV positron linac that normally provide positrons to the positron accumulator ring (PAR). A transport line that bypasses the PAR will bring the electrons to the undulator test area. Characterization techniques will be discussed for the electron beam with a normalized, rms emittance of <10 &pgr; mm mrad (1&sgr;) at micropulse charges of up to 350 pC and micropulse durations of ∼5 ps (FWHM). Preservation of such beam properties, will be critical. The diagnostics planned, with resolutions in parentheses, include the beam position monitors based on stripline pickups (100 &mgr;m), current monitors based on a transformer (60 &mgr;A), beam profile monitors (25 &mgr;m FWHM), and bunch length monitor based on a streak camera (2 ps). Tests proposed include measurement of particle beam transport effects (at one‐tenth the storage ring beam rigidity) caused by small undulator field errors.

ISSN:0094-243X    

DOI:10.1063/1.46964

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

To detect the position of lower intensity beams, the gain of a beam position monitor needs to be increased, and the bandwidth also needs to be reduced in order to suppress noise. The increased gain and reduced bandwidth often result in the instability of instrument zero. To solve this problem, the conventional signal processing scheme of one‐step AM‐to‐PM conversion is modified into a two‐step conversion of AM‐to‐&Dgr;/&Sgr; and then &Dgr;/&Sgr;‐to‐PM. The signal amplification, filtering, and frequency down‐converting are done between the two conversions. As the result, the zero‐drift caused by the changes in channel balance is reduced.

ISSN:0094-243X    

DOI:10.1063/1.46966

出版商:AIP    

年代:1994

数据来源: AIP