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1 BROOKHAVEN SCIENCE ASSOCIATES
Lonny Berman and Dario Arena, NSLS
Summary
The present built-out NSLS-II design includes:
• 30 bending magnet ports, each offering a spectrum with a critical energy of 2.4 keV, similar in quality (flux and brightness) to the ALS bending magnet (not Superbend) spectrum which has a critical energy of 3 keV, but about 3 stronger.
• 8 straight sections containing damping wigglers whose fields will be fixed at 1.8 T, giving an on-axis critical energy of 10.8 keV. The total wiggler length in each of these straight sections is 7 m.
NSLS-II Bending Magnet and Damping Wiggler Beamlines
2 BROOKHAVEN SCIENCE ASSOCIATES
Flux Spectra for NSLS-II Sources and NSLS Bending Magnet Sources
1012
1013
1014
1015
1016
Flu
x [p
hoto
ns/s
ec/0
.1%
bw
/mra
d]
10 eV 100 eV 1keV 10keV 100keV
Photon Energy
Wigglers
VUVhcrit
NSLS-II DW100-1.8T,B=1.8T, 100mm,L=7m, K=16.8
NSLS-II, 25m-radius bend,B=0.4T, Ec=2.39keV
Bending magnets
NSLS-II DW100-1.8T,B=1.8T, 100mm,L=2m, K=16.8
NSLS-I 6.88m-radius bend,B=1.36T, Ec=7.09keV
NSLS-II SCW,B=3.5T, 60mm,L=1m, K=19.6
NSLS-II SCW,B=6T, 60mm,L=1m, K=33.6
NSLS-I 1.91m-radius bend,B=1.41T, Ec=612 eV
3 BROOKHAVEN SCIENCE ASSOCIATES
Brightness Spectra for NSLS-II Sources and NSLS Bending Magnet Sources
1012
1013
1014
1015
1016
1017
1018
1019
Bri
ghtn
ess
[pho
tons
/sec
/0.1
%bw
/mra
d2 /m
m2 ]
10 eV 100 eV 1keV 10keV 100keV
Photon Energy
Wigglers
VUVhcrit
NSLS-II DW100-1.8T,B=1.8T, 100mm,L=7m, K=16.8
NSLS-II, 25m-radius bend,B=0.4T, Ec=2.39keV Bending magnets
NSLS-II DW100-1.8T,B=1.8T, 100mm,L=2m, K=16.8
NSLS-I 6.88m-radius bend,B=1.36T, Ec=7.09keV
NSLS-II SCW,B=3.5T, 60mm,L=1m, K=19.6
NSLS-II SCW,B=6T, 60mm,L=1m, K=33.6
NSLS-I VUV 1.91m-radius bend,B=1.41T, Ec=612eV
4 BROOKHAVEN SCIENCE ASSOCIATES
Distinguishing Source Characteristics and Our Strategy for Their Use
(1) NSLS-II bending magnet sources are very bright from low energies up to hard x-ray energies, and will require only minimal shielding as their spectra are relatively soft
(2) Assign bending magnet sources to address needs from infrared up to about 10 keV, many of which require high brightness (but not exceptionally high brightness which could be satisfied only via access to undulator sources)
(3) Damping wiggler sources will have exceptional power (up to 65 kW) and will be prodigious flux emitters to very high x-ray energies, and will require significant shielding (23 mm lead for side panel of FOE, 50 mm lead for downstream panel of FOE)
(4) Assign damping wiggler sources to address hard x-ray needs (5-50 keV), in particular those that require high flux, large beam sizes, and tunable beams
5 BROOKHAVEN SCIENCE ASSOCIATES
A Suggested NSLS-II Beamline Distribution
(for Bending Magnet and Damping Wiggler Beamlines)
Technique Bending Magnet Damping Wiggler
infrared up to 10 0
VUV/soft x-ray photoemission, circular dichroism,
EXAFS/NEXAFS, microscopy
6 0
tender x-ray EXAFS, photoemission, XSW
2 0
x-ray diffraction, scattering, spectroscopy (single crystal,
catalysis)
3 0
R&D, radiometry 2 0
hard x-ray EXAFS 0 6
hard x-ray powder diffraction, topography, time-slicing,
footprinting
0 4
*This suggested distribution still leaves available 7 bending magnet ports and 3 damping wiggler ports which could each supply canted wiggler x-ray beams.
6 BROOKHAVEN SCIENCE ASSOCIATES
Conceptual Layout of VUV / Soft X-Ray Bending Magnet Beamline
Bending Magnet
Cylindrical Collimating Mirror
Plane Mirror
Plane Grating
Exit Slit
Elliptical Mirror
Refocusing Mirror
ExperimentalStation
A Soft X-Ray Microscope
7 BROOKHAVEN SCIENCE ASSOCIATES
Detector
Sample
Collimating MirrorBe
Window
ApertureAperture
Aperture
Be Window
Focusing MirrorDouble Crystal Mono
Bending Magnet
Micro Focusing Mirror (optional)
Conceptual Layout of Hard X-Ray Bending Magnet Beamline
8 BROOKHAVEN SCIENCE ASSOCIATES
Canted Damping Wiggler Beamlines
• It appears feasible, in the present NSLS-II design, to accommodate canted damping wigglers in individual straight sections (by dividing the 7 m total wiggler length among shorter wigglers), whose radiation emissions are canted by a few milliradians with respect to each other, increasing the number of potential damping wiggler ports.
• The larger the canting angle, the larger the impact on the emittance of the ring. E.g. the emittance grows by 12% if two 3.5 m long wigglers canted by 3 mrad with respect to each other are installed in each of these 8 straight sections.
3 mradCritical Energy
Dependence Across Each Canted Wiggler
Radiation Fan
Ec = Ec,max(1-[ө/өmax]2)1/2
өmax = K/γ10.8 keV
9 BROOKHAVEN SCIENCE ASSOCIATES
Detector
Sample
Collimating Mirror
Double Crystal Mono
Be Window
DampingWiggler
DampingWiggler
ApertureAperture
Aperture
ApertureBe Window
Sample
Detector
Focusing MirrorFocusing Mirror
Double Crystal MonoBe Window
Conceptual Layout of Two Canted Damping Wiggler Beamlines
Lower X-Ray Energy Beamline
Higher X-Ray Energy Beamline
10 BROOKHAVEN SCIENCE ASSOCIATES
Layout of Enclosures for Two Canted Damping Wiggler Beamlines
FOE for canted damping wiggler
beamlines
FOE for bending magnet beamline
Experimental stations for damping wiggler
beamlines
Experimental station for bending magnet beamline
11 BROOKHAVEN SCIENCE ASSOCIATES
A Peek Inside the Enclosures for Canted Damping Wiggler Beamlines
12 BROOKHAVEN SCIENCE ASSOCIATES
Relatively Few Challenges for Bending Magnet Beamlines
(1) Existing NSLS bending magnet beamline components should be transferrable to NSLS-II bending magnet beamlines without much difficulty, provided they are of proper size, possibly with the exception of focusing mirrors
(2) Existing NSLS bending magnet endstation components should also be transferable to NSLS-II bending magnet endstations
(3) Even monochromatic x-ray beam hutches (if needed) might be transferable, if worth the cost to do so (original construction cost might not differ significantly from dismantling/transportation/reconstruction cost)
13 BROOKHAVEN SCIENCE ASSOCIATES
A Lot of Challenges for Canted Damping Wiggler Beamlines
(1) Shielding issues for independent canted damping wiggler beamlines, e.g. shutters and scatter shields which act on one beam and not the other: need design and radiological calculation attention, especially in the front ends and FOEs
(2) Component designs for independent canted damping wiggler beamlines: interference issues and heat load issues
(3) If canting isn’t pursued, can a beamline handle the output of a single 7 m long damping wiggler? The power output of 65 kW will be unprecedented for a permanent magnet wiggler (the APS sector 11 wiggler produces 8 kW for K=14, SPring-8 BL08W wiggler produces 14 kW for K=10). The power density is about half that of the 14 mm period superconducting undulator at its highest K. Power reduction measures (filters, pre-mirrors) will have to be considered. Even if the 7 m of available length is divided among shorter canted damping wigglers, these issues are still significant and will merit careful investigation.
14 BROOKHAVEN SCIENCE ASSOCIATES
SR Wiggler Absorber
Wiggler Absorber
The wiggler absorber clips the radiation fan by about 1 mrad on each side to shadow the downstream exit port. The total intercepted power is 11.6 kW out of 64.6 kW.
The absorber is cantilevered from the upstream flange to allow thermal expansion during bakeout.
Glidcop
15 BROOKHAVEN SCIENCE ASSOCIATES
Maximum temperature (ºC)
397
Cooling wall temperature (ºC)
187
Maximum von Mises stress (MPa)
427
SR Wiggler Absorber – FE Thermal Analysis
About 15 - 20% of the incident power is reflected or scattered. Therefore, the maximum surface temperature is expected to be less than 337ºC.