E. Kahana

Beam position monitor data acquisition for the Advanced Photon Source

This paper describes the beam position monitor (BPM) data acquisition scheme for the Advanced Photon Source (APS) storage ring. The storage ring contains 360 beam position monitors distributed around its 1104-meter circumference. The beam position monitor data acquisition system is capable of making turn-by-turn measurements of all BPMs simultaneously. It is VXI-based with each VXI crate containing the electronics for 9 BPMs. The VXI local bus is used to provide sustained data transfer rates of up to 13 mega-transfers per second to a scanner module. The system provides single-bunch tracking, bunch-to-bunch measurements, fast digital-averaged positions, beam position history buffering, and synchronized multi-turn measurements. Data is accessible to the control system VME crates via an MXI bus. Dedicated high-speed ports are provided to supply position data to beam orbit feedback systems.<<ETX>>

Initial diagnostics commissioning results for the Advanced Photon Source (APS)

Principal diagnostics systems have been installed and nearly all have been commissioned on the subsystems of the Advanced Photon Source (APS) facility. Data have been obtained on beam position, beam profile, current, beam loss rate, and synchrotron radiation monitors on both injector rings and most recently the main 7-GeV storage ring. Results for the 150- to 450-MeV electron beams in the accumulator ring, up to 7 GeV in the injector synchrotron, and 4.5 to 7 GeV in the SR will be presented.

Overview of charged‐particle beam diagnostics for the advanced photon source (APS)

Plans, prototypes, and initial test results for the charged-particle beam (e[sup [minus]],e[sup +]) diagnostic systems on the injector rings, their transport lines, and the storage ring for the Advanced Photon Source (APS) are presented. The APS will be a synchrotron radiation user facility with one of the worlds brightest x-ray sources in the 10-keV to 100-keV regime. Its 200-MeV electron linac, 450-MeV positron linac, positron accumulator ring, 7-GeV booster synchrotron, 7-GeV storage ring, and undulator test lines will also demand the development and demonstration of key particle-beam characterization techniques over a wide range of parameter space. Some of these parameter values overlap or approach those projected for fourth generation light sources (linac-driven FELs and high brightness storage rings) as described at a recent workshop. Initial results from the diagnostics prototypes on the linac test stand operating at 45-MeV include current monitor data, beam loss monitor data, and video digitization using VME architecture.

Configuration and test of the APS storage ring beam position monitor electronics

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.

Local beam position feedback experiments on the ESRF storage ring

This paper describes the results of local beam position feedback experiments conducted on the ESRF storage ring using digital signal processing (DSP) under the trilateral agreement of collaboration among ESRF, APS, and SPring-8. Two RF beam position monitors (BPMs) in the upstream and downstream of the insertion device (ID) and two X-ray BPMs in the sixth cell were used to monitor the electron beam and the X-ray beam emitted from the ID, respectively. The local bump coefficients were obtained using the technique of singular value decomposition (SVD) on the global response matrix for the bump magnets and all the available BPMs outside the local bump. The local response matrix was then obtained between the two three-magnet bumps and the position monitors. The data sampling frequency was 4 kHz and a proportional, integral, and derivative (PID) controller was used. The result indicates the closed-loop feedback bandwidth close to 100 Hz and clear attenuation (/spl ap/-40 dB) of the 7-Hz beam motion due to girder vibration resonance. Comparison of the results using the RF BPMs and X-ray BPMs will be also discussed.

Beam position monitor calibration for the Advanced Photon Source

This paper describes the sensitivity and offset calibration for the beam position monitors (BPMs) using button-type pickups in the injector synchrotron, storage ring, and insertion devices of the Advanced Photon Source (APS). In order to reduce the overall offset and to isolate the error (/spl lsim/100 /spl mu/m) due to the low fabrication tolerance in the extruded storage ring vacuum chamber, the electrical offset is minimized by carefully sorting and matching the buttons and cables according to the button capacitance and the characteristic impedances of the cable and the button feedthrough. The wire method is used for the sensitivity calibration, position-to-signal mapping, and measurement of resolution and long-term drift (/spl lsim/1 mV) of the processing electronics. The processing electronics was also tested at Stanford Synchrotron Radiation Laboratory (SSRL) using a real beam, with results indicating better than 25 /spl mu/m resolution for the APS storage ring. Conversion between the BPM signal and the actual beam position is done by using polynomial expansions fit to the mapping data with absolute accuracy better than 25 /spl mu/m within /spl plusmn/5 mm square. Measurement of the effect of button mispositioning and mechanical inaccuracy of the extruded storage ring vacuum chamber, including deformation under vacuum, will be also discussed.<<ETX>>

Diagnostics for the APS undulator test line

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 π mm mrad (1σ) 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 μm), current monitors based on a transformer (60 μA), beam profile monitors (25 μm FWHM), and...

Deisgn of the APS transverse and longitudinal damping system

The three stripline damper system designed to reduce instability growth in the Advanced Photon Source Storage ring is described. The main sources of instability growth are higher‐order modes of the accelerating cavities and the resistive wall impedance of the small insertion devices beam tubes. The transverse damping system will be dominated by the resistive wall modes and the longitudinal damper will reduce the higher‐order modes from the accelerating cavities. Three stripline units will be used: One as a pickup, one as a transverse damper, and one as a longitudinal damper. They will each contain four strips located symmetrically about the vertical center plane at the top of an elliptical beam tube and two located at the bottom. (AIP)

Initial diagnostics commissioning results for the APS injector subsystems

In recent months the first beams have been introduced into the various injector subsystems of the Advanced Photon Source (APS). An overview will be given of the diagnostics results on beam profiling, beam position monitors (BPMs), loss rate monitors (LRMs), current monitors (CMs), and photon monitors on the low energy transport lines, positron accumulator ring (PAR), and injector synchrotron (IS). Initial measurements have been done with electron beams at energies from 250 to 450 MeV and 50 to 400 pC per macrobunch. Operations in single turn and stored beam conditions were diagnosed in the PAR and IS.

Tune measurement in the APS rings

The APS system will contain three rings. The first is a positron accumulator ring(PAR). Its function is to coalesce 24, 30-ns-long positron bunches into one 290-ps bunch. The second is the injector synchrotron (IS). It accelerates the 450-MeV positron bunches to 7 GeV for injection into the storage ring(SR). Five IS bunches are accumulated into one SR bucket to produce 17.5-nC, 60-ps bunches. Twenty buckets will be filled in the SR to give a current of 100 mA.<<ETX>>