Infrared Extraction Update L. Carr, D. Arena, A. Blednyk, S. Coburn, V. Ravindranath and NSLS-II Team NSLS-II EFAC Review May 2007

BROOKHAVEN SCIENCE ASSOCIATES Infrared Outline NSLS-II Infrared beamlines and requirements: quick refresher Infrared Extraction: –revised extraction geometry* –large gap dipoles (excellent long-wavelength performance). –1 st mirror heat load* Performance Figures Beamline locations (brief)* Environment (noise: vibration, EMI, etc.) –stability taskforce & workshop requirements Top-off issues* Bunch structure(s) for timing *addresses specific EFAC concerns and recommendations

BROOKHAVEN SCIENCE ASSOCIATES Science and IR Source Requirements Biological, Chemical, Environmental, Materials, Space … –4000 cm -1 ( =2.5  m) to < 400 cm -1 ( =25  m) mid and far-IR microprobe mid-IR chemical imaging (raster scanning  area imaging) –Imaging needs an extended source to optimally illuminate. Materials (especially under extreme conditions) –Mostly “single point” spectroscopy high pressures and temperatures laser pump-probe cryospectroscopy high magnetic fields, spin resonance –4000 cm -1 down to ~ 2 cm -1 ( =5 mm) mid-IR standard port far-IR large port

BROOKHAVEN SCIENCE ASSOCIATES Mid-IR Extraction: Standard Dipole Chamber with 24mm high interior Plane 1st mirror, with slot 14 mrad V (avg.) by 50 mrad H –small reduction in  V compared to internal toroidal mirror extraction Collects dipole and 0° edge radiation Other details to be determined: –required slot length to allow x-rays to pass –beam impedance –mechanical mirror mounting –mirror cooling (back or end surface) care to avoid sources of vibration Standard NSLS-II Dipole “conventional” extraction S. Coburn

BROOKHAVEN SCIENCE ASSOCIATES FIR and mm-wave Extraction: Large Gap Dipole Chamber S. Coburn Chamber with 78mm high interior Plane 1st mirror, with slot 42 mrad V (avg) by 50 mrad H –small reduction in  V compared to internal toroidal mirror extraction, but less risk from waveguide cutoff effects (shorter distance) Collects dipole and 0° edge radiation Other details to be determined: –required slot length to allow x-rays to pass – beam impedance –mechanical mirror mounting –mirror cooling (back or end surface) care to avoid sources of vibration Large Gap Dipole View into exit port Special chamber construction S. Coburn e e Have adopted largest of proposed dipole designs

BROOKHAVEN SCIENCE ASSOCIATES Mid-IR Brightness NSLS II VUV/IR

BROOKHAVEN SCIENCE ASSOCIATES Far-IR Brightness cutoff effect due to chamber shielding c ~ ( h 3 /  ) 1/2

BROOKHAVEN SCIENCE ASSOCIATES Initial FEA Analysis of Surface Deformation New extraction: Beam no longer at grazing incidence onto 1 st collection/extraction mirror. Calculation with internal H 2 O cooling, no slot: –Relative longitudinal error = 3  m –Relative transverse error = 8  m V. Ravindranath Conclusion: will need slot 500ma, 3.6 GeV

BROOKHAVEN SCIENCE ASSOCIATES Locations for IR Extraction Standard dipole Mid-IR ports: can be placed in proximity to related science activities (not constrained by accelerator symmetry requirements). Large gap dipole Far-IR ports: Large gap dipoles limited to 3 symmetric locations around ring. Both dipoles in a DBA cell, but typically only 2 nd dipole available for IR extraction (due to ID upstream of 1 st dipole). Plan to locate 1 large-gap dipole cell-pair downstream of RF straight section (no ID, can use both dipoles for IR). Result: maximum of 4 far-IR extractions. (prefer downstream of RF, not injection) Beamline floor plans: TBD “exaggerated” NSLS-II with 3 long straights, showing a symmetric arrangement of large-gap dipole pairs. candidate location for large gap dipole cell

BROOKHAVEN SCIENCE ASSOCIATES IR Requirements for Stability Taskforce & Report Stability of electron beam through dipoles: Specification request: –Position: 1  m V, 3  m H –Angle: 3  rad V, 6  rad H Corresponds to 7% of beam size (compare to 10% overall NSLS-II specification). Requirement defined to deliver: –minimum 300:1 S/N in worst-case-scenario –would be ~ 30X better than existing NSLS VUV/IR –frequency range up to 20 kHz. Can benefit from even better stability (additional 30X will put noise near background for essentially all measurements).

BROOKHAVEN SCIENCE ASSOCIATES NSLS II Infrared Capacity In most cases, 2 nd dipole of DBA cell is potential IR extraction location. –Slot in 1 st mirror should allow for a downstream soft x-ray (BM) beamline. –3-pole wiggler & IR edge extraction probably incompatible (both a 0 ° and angular pattern approaching 1/  ). Mid-IR: plan to develop beamlines 5 beamlines on 3 separate extractions: –H = 50 mrad & V ~ 14 mrad (avg.) –Special chambers required, but otherwise standard dipole (flexibility). Single extraction port can serve 2 or 3 microprobe endstations. Or entire 50 mrad horizontal can serve a single FPA imaging spectrometer –3 ports  1 split into 3 microprobes, 2 for FPAs = 5 beamlines. Can add more ports for growth. –Plan to locate in proximity to other Biological / Imaging beamlines (e.g.  XRF,  XANES). Far-IR / THz / mm-waves: plan to develop 3 beamlines on 3 separate extractions (max = 4): –H = 50 mrad & V ~ 42 mrad (avg.) –Special chambers and special large-gap dipole magnets –Single endstation per extraction. –Locations constrained by 3-fold ring symmetry and RF straight

BROOKHAVEN SCIENCE ASSOCIATES Top Off Issues NSLS-II injection approximately once per minute: –expect some beam motion for ~ 1 second IR spectrometer data collection “styles”: 1.long scan time, averaging many short (< 1 second) scans 2.raster scan imaging (~ 1 minute per point, but ~ 1000 points) 3.ultra-high resolution spectroscopy (> 5 minutes for single scan). Software: – macros and VB scripts to monitor “beam available” signal, pause collections. (R. Smith: testing a script to see how 1 and 2 can be managed). –more work necessary for 3.

BROOKHAVEN SCIENCE ASSOCIATES RF Buckets, Bunches and Timing Infrared has been one of the key users of the storage ring bunch structure for time-resolved studies (methods dependent on bunches themselves). –no benefit from crab cavities, indirectly from laser slicing (CSR) –not limited to IR … all techniques where beam is not resolvable and fast detection not sufficient. Issues: –Bunch lengths (  BL for NSLS II will be 10s of picoseconds) –Pulse Rep. Frequencies (PRFs) & synchronization to mode-locked lasers MHz RF, ring circumference = 792m, harmonic number = 1320    x   x  x  x  x   Mode-locked Ti:sapphire prefers 76 to 82 MHz, 75 to 100 MHz for Nd:YLF, more options with fiber lasers –note: 500MHz/6  PRF= 83.3 MHz –Jitter (bunches relative to RF, to each other) below 10% of bunch RMS, especially for frequencies > 1 kHz. sets NSLS-II RF phase system stability requirements – stringent, but possible. –Harmonic cavity effects, de-tuned operations, low-  lattices: Still to be investigated.

BROOKHAVEN SCIENCE ASSOCIATES Symmetric Fills and PRFs for NSLS-II h=1320

BROOKHAVEN SCIENCE ASSOCIATES Summary Updated Infrared extraction –more conventional side-extraction, 1 st plane mirror, with slot to allow x-rays through. –very large gap dipoles, unsurpassed far-IR performance for incoherent SR. –generally higher mid-IR brightness than existing NSLS VUV/IR, expect high stability too. Capacity: –Plan to develop 3 extractions each (mid-IR & far-IR) during early phases of NSLS II operations. corresponds to 8 beamline endstations, compare to existing 6 on NSLS VUV/IR –Potential for growth (especially mid-IR). Stability: –Requirements to achieve S/N at least 30X better than NSLS VUV/IR. –More is better! Pulse Repetition Frequencies (PRFs): –h=1320, booster at 1/5 th for efficient filling of NSLS-II ring in top-off. Needing more attention: detailed impact of top-off injection on various IR measurement methods.