Recent APS Storage Ring Instrumentation Developments Glenn Decker Advanced Photon Source Beam Diagnostics March 1, 2010
Ring Diagnostics Overview RF beam position monitor technology Photon beam position monitor technology Photon counting applications
APS Beam Stability Goals Note that APS rms vertical beam size is 8.5 microns Photon angular divergence 1 / ( N) approaching 5 rad Typical stability requirements set at 5-10% of beam size / divergence.
APS Broadband RF BPM data acquisition upgrade Eight channels/board, 88 MS/sec sampling. Altera FPGA processing. One second (262144 samples) turn by turn beam history for machine studies / fault diagnosis. Demonstrated noise floor < 5 nm / Hz Fantastic post mortem capability True individual bunch position monitor
State-of-the-art Commercial Solution Noise floor approaching 2 nm / Hz. Long term drift 200 nm p p/ 24 hours*. * Guenther Rehm, Diamond Light Source, EPAC 2008
Storage Ring Insertion Device Vacuum Chamber Pickup Electrodes 02/27/10
BPM Electronics Performance Libera Brilliance@APS APS BSP-100 Module DC is not a frequency, it is a limit.
millihertz
APS Front-end hard x-ray beam position monitor developments Extensive studies have taken place at the APS investigating copper x ray fluorescence vs. photoemission for photon beam position monitoring. Soft bending magnet radiation background essentially eliminated. High power densities remain a challenge. An in air prototype of a device of this type has been installed at 35 ID and is undergoing extensive testing.
Typical Photoemission-based Photon BPMs APS Insertion Device Bending Magnet (Vertical Only) 02/27/10
Grazing-incidence Hard X-ray Fluorescence-Based Insertion Device X-ray Beam Position Monitor Conceptual Design (GRIID-XBPM) Concept courtesy of Bingxin Yang
Power Density Profiles @ 30 m, APS undulator A, 100 ma Courtesy of Roger Dejus
Prototype In-air GRID-XBPM @ 35-ID Bingxin Yang Four Pin diodes (Two sets, top and bottom) Pinhole camera apertures X-rays Beam stop (PS2 surrogate) With pin diode monitoring X-ray transmission.
Hard X-ray BPM Signal Variation with Vertical Position
Conceptual Design of the first article GRIIDXBPM 44 Outlet Detail 1.5 mm 0.25 mm 3.0 mm Courtesy of Soon-Hong Lee, AES-MED
Simulation Result (Preliminary) - Vertical Temperature Distribution @ Case 4 (Max. 134.7 C) Stress Distribution @ Case 3 (Max. 218.3 MPa) Note: 10 kw = 5 m Undulator A @ 100 ma ~ 11.3 µm bump Surface deflection @ Case 1 (Horizontal direction only, 2100x) Courtesy of Soon-Hong Lee, AES-MED
High dynamic range bunch purity monitor APD electronic improvement reduces the dark counts Signal to noise ratio above 10 11 :1 Impurity profile shows the halo inside the PAR fundamental bucket Observed rare event of two turn extraction (near 36 th bucket) Potential applications: studies of very low intensity beam halo 02/27/10
X-ray wire scanner: Development of a bunch-bybunch beam transverse profiler Replacing the solid target with copper wires scanning across monochromatic undulator beam, the spatialtime resolved counts yield bunch specific beam profiles. They are especially useful for users using Bunch 0 of hybrid fill. Vertical and horizontal wires give the x yprofiles, slanted wires measure the tilt angle of the x ray beam cross section. 02/27/10
TCSPC: development of a bunch-by-bunch beam longitudinal profiler A high temporal resolution, Linux compatible commercial time correlated single photon counting (TCSPC) unit is used to acquire longitudinal profiles during user runs, bunch by bunch. This is important for hybrid mode timing users. Bunch phase and RMS length are to be extracted at 8 16 seconds intervals and made into process variables, available facility wide. 02/27/10
APS Storage Ring Diagnostics Summary Instrumentation supporting AC beam stability is well in hand. Long term drift is quite challenging at the sub micron scale. Photon bpm technology is evolving. Photon counting techniques provide several powerful tools associated with a beam diagnostics dedicated beamline Bunch purity w/ 10^11 dynamic range Bunch by bunch transverse profiles Bunch by bunch longitudinal profile
Tunnel temperature issues / solutions APS Tunnel Air / Water temperature regulation is pretty good, at the level of 0.6 1.0 deg. F p pfor air, and 0.1 deg. F p pfor water. Improving this significantly will likely be expensive. Investigations are underway to develop mechanical sensors to monitor the physical location of critical beam position monitor pickups: A BPMPM (BPM 2 ). Correlation of measured beam position and water temperature ID Chamber BPM Pickup Electrode 0.5 m / 0.1 deg.f
Tunnel temperature issues / solutions Laser proximity sensor 1 deg. C Temperatures Deg. C Cyan= Air Red= Stand Green= BPM Yellow= Thick Chamber Blue = Thin Chamber Vertical Position m Red = Chamber Center Blue = BPM Block Keyence Proximity Sensor, 50 nm resolution * Data courtesy of Bob Lill
Decker Distortion Stray radiation backgrounds affecting insertion device photoemission based photon bpms can be reduced by girder realignment. Residual systematic errors can be reduced to the 10 20 m level. 34-ID after girder realignment 02/27/10