1. 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

2. 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

3. Science and IR Source Requirements
Biological , Chemical, Environmental, Materials, Space …
4000 cm-1 (l=2.5 mm) to < 400 cm-1 (l=25 mm)
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 (l=5 mm)

4. Mid and Far Infrared Microspectroscopy & Imaging
Imaging (anticipate growth of this technique)
Microprobe (anticipate continued demand)
Fluid l=3mm | Miller et al
Forsterite (Fo100)
Clino-enstatite
Wavelength (mm)
Absorbance
L2005*A4

5. Science Requirements: THz / mm waves & Magnetism
Antiferromagnetic Resonance in LaMnO3
Multiferroics A. Sirenko et al
D. Talbayev & L. Mihaly, Stony Brook
PRL 93 (July ‘04), PRB 69 (‘04)
H=12T

6. Edge Radiation: viable alternative?
Intensity
low
high
Edge radiation emitted at transitions entering/exiting dipole magnets.
Intrinsically bright, emission into 1/g.
Radial polarization (complication).
Issues:
two-edge interference, cancellation on-axis (U13 results in agreement).
chamber cutoff due to narrow emission. Source radial size is lg.
For E = 3 GeV, source size at l = 1mm is 6 meters (!)
insufficient data to confirm cutoff effect.
Not an extended source: Problems illuminating entire FPA detector.
lg ~ chamber dimension
G.P. Williams et al, to be submitted

7. Infrared Extraction Schematic: NSLS II Dipole Bend
NSLS II bend radius r = 25 meters
qrms= (3l/4pr)1/3
Requirements for full angle (2xqrms)
l = 6 mm -> 8 mrad
l = 100 mm -> 20 mrad
l = 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/g stripe) -> lower than 570 W/cm2 of NSLS U4IR, may not need slot or protective mask
Note: does not consider edge radiation component
M1 Toroid M2
Plane
Note: includes 0° edge source
2.6 meters
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)

8. NSLS II Infrared Extraction: Toroidal First Mirror
Initial optical analysis:
= 6 mm (1600 cm-1)
R&D:
mirror mat’l, finite element analysis
surface figure, tolerances.
range of adjustment, sensitivity to errors
Toroidal mirror
Source points along electron orbit

9. Mid-IR for Chemical and Biological mProbe 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

10. Magnetospectroscopy & Millimeter Spectral Range
Magnetic resonance 1 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%.

11. Infrared Beamline Schematic
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, mscopes)
mostly from NSLS VUV/IR with assumption that they are being maintained at “state-of-the-art”.
Hutch Enclosure 3 2
Matching & Stabilization Optics
Spectrometer & Endstation(s) 1 e
Hutch services to include
dry N2 gas and lN2
Diamond Window
Dipole Bend
Imaging Microscope w/FPA or
Cryostat / Magnet / Hi-Pressure cell
Extraction Optics

12. Infrared Beamline Schematic (divided 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).
Hutch Enclosure(s)
Matching & Stabilization Optics e
Hutch services to include
dry N2 gas and lN2
Diamond Window
Dipole Bend
2 or 3 mprobe endstations
independently operating
20x20mrad to 12x12mrad (standard gap extraction)
Extraction Optics

13. 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).

14. 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?

15. 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).

16. 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 (sBL for NSLS II will be 10s of picoseconds)
Pulse Rep. Frequencies & Synchronization to mode-locked lasers
500 MHz RF, harmonic number = (=2*2*5*5*13)
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?

17. 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.