# Presentation: 507088

## Infrared Experimental Facilities for NSLS II

- Larry Carr
- for the NSLS II Team: esp. D. Arena, A. Blednyk, J. Hill, C. Homes, S. Hulbert, E. Johnson,  L. Miller, S. Pjerov
- NSLS - Brookhaven Nat’l Lab

## Infrared Outline

- Science & Technique Requirements for IR Beamlines (brief)
- Getting the Required Performance from NSLS II
- Special Optics
- Beamline layout / schematic : endstation instrumentation
- Environment (noise: vibration, EMI, etc.)
- Short bunches and timing

## 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 and Far Infrared Microspectroscopy & Imaging

- Fluid inclusions @ =3m   |  Miller *et al*

**Mid and Far Infrared Microspectroscopy & **_**Imaging**_

_*Microprobe*_ (anticipate continued demand)

_*Imaging*_ (anticipate growth of this technique)

## Science Requirements:  THz / mm waves & Magnetism

- H=12T

- Antiferromagnetic Resonance in LaMnO3

- D. Talbayev & L. Mihaly, Stony Brook
- PRL **93 **(July ‘04), PRB **69** (‘04)

## Edge Radiation: viable alternative?

- Edge radiation emitted at transitions entering/exiting dipole magnets.
- Intrinsically bright, emission into 1/**.
- Radial polarization (complication).
- Issues:
- two-edge interference, cancellation on-axis (U13 results in agreement).
- chamber cutoff due to narrow emission.  Source radial size is **.
- 	For E = 3 GeV, source size at  = 1mm is 6 meters (!)
- insufficient data to confirm cutoff effect.
- _Not_ an extended source: Problems illuminating entire FPA detector.

- G.P. Williams *et a*l, to be submitted

## Infrared Extraction Schematic: NSLS II Dipole Bend

- NSLS II bend radius **  25 meters
*****rms*= (3**4**)1/3
*Requirements for full angle (2x****rms**)*
**6 m		8 mrad
**100 m		20 mrad
**2 mm		54 mrad

- Power load on 1st mirror = 1.2 kW(low critical energy of NSLS II bends helps)
- Power _density_ ~ 390 W/cm2  (narrow 1/ stripe) lower than 570 W/cm2 of NSLS U4IR, may not need slot or protective mask
*Note:* does not consider edge radiation component

- Enables large horizontal collection of ~ 50 mrad
- Standard dipole chamber  16 mrad vertical  (suitable for mid-IR, can divide horizontal)
- Large gap magnet dipole chamber  32 mrad vertical (needed for far-IR)

## NSLS II Infrared Extraction:  Toroidal First Mirror

**NSLS II Infrared Extraction:  Toroidal First Mirror**

- Initial optical analysis:
-  6 m  (1600 cm-1)

- Source points along electron orbit

- Toroidal mirror

- _R&D:_
- mirror mat’l, finite element analysis
- surface figure, tolerances.
- range of adjustment, sensitivity to errors

## Mid-IR for Chemical and Biological Probe and Imaging

- NSLS II outperforms existing VUV/IR for brightness over most of mid-IR due to lower emittance.  Essentially same mid-IR performance for Standard and Large Gap dipoles.

- NSLS II

- VUV/IR

## Magnetospectroscopy & Millimeter Spectral Range

- Magnetic resonance1 T  1 cm-1 for typical spin.
- Standard NSLS-II dipole and chamber yields ***less than 2%*** of the flux from the VUV Ring at 3 cm-1.
- NSLS II Large Gap provides 37% of VUV ring (@ 3 cm-1).  Could be made *better than VUV* by increasing vertical dimension another 50%.

## Infrared Beamline Schematic

**Infrared Beamline Schematic**

*e*

- Hutch services to include
- dry N2 gas and N2

- Imaging Microscope w/FPA
*or*
- Cryostat / Magnet / Hi-Pressure cell

- Dipole Bend

- ExtractionOptics

- Diamond Window

- Matching & StabilizationOptics

- Spectrometer & Endstation(s)

- Hutch Enclosure

- 1

- 2

- 3

- IR Beamlines consist of 3 “sub-systems”
- Extraction (new components for NSLS II)
- Optical Matching and Transport (mostly new for NSLS II)
- End-station Instruments (e.g., spectrometers, cryostats, scopes)
- mostly from NSLS VUV/IR with assumption that they are being maintained at “state-of-the-art”.

## Infrared Beamline Schematic (divided extraction)

**Infrared Beamline Schematic (divided extraction)**

*e*

- Dipole Bend

- ExtractionOptics

- Diamond Window

- Matching & StabilizationOptics

- Hutch Enclosure(s)

- Hutch services to include
- dry N2 gas and N2

- 2 or 3 probe endstations
- independently operating
- 20x20mrad to 12x12mrad(standard gap extraction)

- Mid IR microprobe endstations can work with 16mrad by 16mrad extraction, so 50mrad of horizontal can be divided into 2 or 3 independently operation beamlines (similar to U10A/B and U2A/B infrared beamlines at NSLS VUV/IR ring).

## NSLS II Infrared Capacity

- Accelerator design includes 5 (=10/2) large (vertical) gap dipole magnets and chambers, and 5 standard dipole chambers, for IR.  All ports will extract both dipole bend and edge radiation.
- Issues:
- detailed dipole chamber design and beam impedance calculations.
- optics for a) extraction and b) matching to instruments and endstations.
- Standard dipole chambers for mid-IR  (five total).
- 50 mrad horizontal.
- 12 to 20 mrad vertical extraction (16 mrad average).
- Up to 3 independent microprobe endstations _or_ 1 FPA imaging endstation.
- Plan to develop mid-IR beamlines on 3 extractions:
- 2 or 3 Microprobe endstations sharing one port (horizontal split).
- 2 FPA Imaging spectrometers each on its own port  (two ports)
- leaves 2 more ports available for growth.
- Located in proximity to other Biological / Imaging beamlines (x-ray).

## NSLS II Infrared Capacity (cont’d)

- Large gap dipole chambers for far-IR (five total).
- 50 mrad horizontal
- 24 to 40 mrad vertical (32 mrad average).
- Single endstation per extraction.
- Plan to develop 3 far-IR beamlines and endstations on 3 extractions:
- Magnetospectroscopy / Spin Resonance
- Extreme pressures (diamond anvil cells, laser heating, cryo).
- Time-resolved (pump-probe with laser, cryo).  Proximity to slicing?
- Capacity for 2 additional (future) beamlines
- Even larger vertical extraction opportunity?

## Illuminating an Imaging FPA Detector with mid-IR Dipole Bend Radiation

- _R&D activity:_
- Dipole bend synchrotron radiation is an extended source when horizontal collection exceeds natural opening angle for emission.
- NSLS II ports will extract 50 mrad horizontal.  Natural angle (diffraction) at 1600 cm-1 is 8 mrad.
- 6 : 1 aspect ratio.
- Develop anamorphic optical system to “re-shape” beam footprint to match FPA.
- Might be a simple spherical mirror used off-axis  (1 meter f.l. at 5 degrees incidence, defocus slightly).

## RF Buckets, Bunches and Timing

- Infrared has been one of the key users of the storage ring bunch structure for time-resolved studies.
- Issues:
- Bunch lengths  (**BL for NSLS II will be 10s of picoseconds)
- Pulse Rep. Frequencies & Synchronization to mode-locked lasers
- 500 MHz RF, harmonic number = 1300 
- Ti:Sapp prefers 76 to 82 MHz, more options with fiber lasers
- note: 500MHz/13  PRF= 38.4 MHz = 76MHz/2
- 2 ns between pulses typically too short (need 10 ns minimum)
- filling 100 symmetric buckets yields 26 ns
- Jitter (bunches relative to RF, to each other) below 5% of bunch RMS
- Compatibility with overall operations
- constraints on current, lifetime, orbit/lattice (iterations with accelerator group)
- Other options for consideration:
- laser slicing and location relative to undulator/modulator.
- crab cavities: not useful for IR?

## Summary

- Infrared extraction design idea developed: challenging optical design, but appears feasible
- higher mid-IR brightness than existing NSLS VUV/IR
- extended dipole source for Imaging / FPA detector based instruments
- competitive very far-IR performance
- Capacity for growth, plus synergy with overall SR community:
- 5 ports _each_ for mid and far IR, plan to develop 3 _each_ during early phases of NSLS II Ops.
- Noise:  need to minimize mechanical and electrical noise.
- low frequency noise from pumps, motors, AC line.
- RF sideband noise: intrinsically smaller with 500 MHz SC RF?
- beam stabilization to remove residual motion.
- goal: 10 to 100 times smaller than existing NSLS.
- Top-off injection: compatible with high spectral resolution measurements?
- Location: (attention paid to lab support facilities and slicing option)
- Hutches: are quite necessary, but typically not for personnel protection.
- control atmospheric (humidity) and acoustic environment.
- laser safety, magnet fields.
- good for optical alignment.