Recent APS Storage Ring Instrumentation Developments Glenn Decker Advanced Photon Source Beam Diagnostics March 1, 2010

Glenn Decker FLS2010 Ring Diagnostics Overview  RF beam position monitor technology  Photon beam position monitor technology  Photon counting applications

Glenn Decker FLS2010 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.

Glenn Decker FLS2010 APS Broadband RF BPM data acquisition upgrade  Eight channels/board, 88 MS/sec sampling. Altera FPGA processing.  One second ( 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

Glenn Decker FLS2010 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

02/27/10 Storage Ring Insertion Device Vacuum Chamber Pickup Electrodes

Glenn Decker FLS2010 BPM Electronics Performance Libera APS BSP-100 Module DC is not a frequency, it is a limit.

Glenn Decker FLS2010 milliHertz

Glenn Decker FLS2010 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.

02/27/10 Typical Photoemission-based Photon BPMs APS Insertion Device Bending Magnet (Vertical Only)

Glenn Decker FLS2010

Grazing-incidence Hard X-ray Fluorescence-Based Insertion Device X-ray Beam Position Monitor Conceptual Design (GRIID-XBPM) Concept courtesy of Bingxin Yang

Glenn Decker FLS2010 Power Density 30 m, APS undulator A, 100 mA Courtesy of Roger Dejus

Glenn Decker FLS2010 Prototype In-air 35-ID X-rays Four Pin diodes (Two sets, top and bottom) Pinhole “camera” apertures Bingxin Yang Beam stop (PS2 surrogate) With pin diode monitoring X-ray transmission.

Glenn Decker FLS2010

Hard X-ray BPM Signal Variation with Vertical Position

Glenn Decker FLS mm 3.0 mm 0.25 mm Conceptual Design of the first article GRIIDXBPM 44” Outlet Detail Courtesy of Soon-Hong Lee, AES-MED

Glenn Decker FLS2010 Simulation Result (Preliminary) - Vertical Temperature Case 4 (Max °C)Stress Case 3 (Max MPa) Surface Case 1 (Horizontal direction only, 2100x) ~ 11.3 µm bump Note: 10 kW = 5 m Undulator 100 mA Courtesy of Soon-Hong Lee, AES-MED

02/27/10 High dynamic range bunch purity monitor APD electronic improvement reduces the dark counts “Signal to noise ratio” above :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-by- bunch beam transverse profiler Replacing the solid target with copper wires scanning across monochromatic undulator beam, the spatial- time-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-y profiles, 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.

Glenn Decker FLS2010 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

Glenn Decker FLS2010 Tunnel temperature issues / solutions  APS Tunnel Air / Water temperature regulation is pretty good, at the level of 0.6 – 1.0 deg. F p-p for air, and 0.1 deg. F p-p for 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 0.5  m / 0.1 deg.F ID Chamber BPM Pickup Electrode

Glenn Decker FLS2010 Tunnel temperature issues / solutions Laser proximity sensor Cyan= Air Red= Stand Green= BPM Yellow= Thick Chamber Blue = Thin Chamber Temperatures Deg. C Vertical Position  m Red = Chamber Center Blue = BPM Block Keyence Proximity Sensor, 50 nm resolution 1 deg. C * Data courtesy of Bob Lill

02/27/10 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