# Presentation: 651769

## Infrared Extraction Update

- L. Carr, D. Arena, A. Blednyk, S. Coburn, V. Ravindranath and NSLS-II Team
- NSLS-II EFAC Review 10-11 May 2007

## Infrared Outline

- NSLS-II Infrared beamlines and requirements: quick refresher
- Infrared Extraction:
- revised extraction geometry*
- _large_ gap dipoles (excellent long-wavelength performance).
- 1st 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*

## 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 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*

## 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***

*Have adopted *_*largest*_* of **proposed dipole designs*

## Mid-IR Brightness

**Mid-IR Brightness**

- NSLS II

- VUV/IR

## Far-IR Brightness

**Far-IR Brightness**

- cutoff effect due to
- chamber shielding
- c ~ (*h*3/**)1/2

## Initial FEA Analysis of Surface Deformation

**Initial FEA Analysis of Surface Deformation**

- New extraction: Beam no longer at grazing incidence onto 1st collection/extraction mirror.
- Calculation with internal H2O cooling, no slot:
- Relative longitudinal error = **3 ********m**
- Relative transverse error  = **8 ********m**

*V. Ravindranath*

- Conclusion:  _will need slot_

*500ma, 3.6 GeV*

## 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 2nd dipole available for IR extraction (due to ID upstream of 1st 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

## 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).

## NSLS II Infrared Capacity

- In most cases, 2nd dipole of DBA cell is potential IR extraction location.
- Slot in 1st 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

## Top Off Issues

- NSLS-II injection approximately once per minute:
- expect some beam motion for ~ 1 second
- IR spectrometer data collection “styles”:
- long scan time, averaging many short (< 1 second) scans
- raster scan imaging (~ 1 minute per point, but ~ 1000 points)
- 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.

## 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
- 499.7 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*.

## Symmetric Fills and PRFs for NSLS-II   h=1320

## Summary

- Updated Infrared extraction
- more conventional side-extraction, 1st _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 1/5th for efficient filling of NSLS-II ring in top-off.
- Needing more attention: detailed impact of top-off injection on various IR measurement methods.