Preliminary
Design Report
Phase I & II Insertion Device
Beamlines
NE-CAT
August 2003
Malcolm Capel
NE-CAT Lead Scientist,
Associate Director for beamline technology
CONTENTS
2.
Design chANGES FROM cONCEPTUAL dESIGN
3. BEAMLINE TECHNICAL SPECIFICATIONS
The
principal aims of the NE-CAT collaboration are the design, construction
and operation of undulator and bending magnet-based beamlines
for biological crystallographic data collection. Said beamlines will
be highly automated, possess
high brilliance and narrow band pass suitable for optimized MAD crystallographic
data collection. The resulting beamlines will
be used mainly in support of NIH National Centers for Research Resource
(NCRR)-funded
core scientific collaborations. The
core scientific collaborations involve a wide range of structural interests
including: biological signal transduction,
DNA transcription (initiation and regulation), cell cycle regulation, virus
structure and function, protein folding and protein synthesis (ribosome structure).
NE-CAT will also reserve a portion of operational time to support biological
crystallography by independent researchers.
The
main technological challenge of the NE-CAT NCRR proposal is the use of the
tandem-offset undulator concept to increase the
number of concurrently-operating undulator beamlines at a single APS sector. We intend to develop three beamlines using the tandem-canted undulator
strategy and a single bending magnet-based beamline. Our current planning is based on use of a pair
of 3.3 cm period undulators, 2.07 meters in length
with an angular offset of 1.0 milliradian. Beamline construction
will be split into four phases, summarized in Table 1.1. Note: for reasons delineated below the order
of construction of the four sector 24 beamlines
and the nomenclature used to refer to them have changed since submission of
the NE-CAT Conceptual Design Report (see first column, Table 1.1).
Table 1.1: Description of NE-CAT Beamlines and
Build-Phases
| Build Phase Designation PDR CDR |
Source |
|
Energy Resolution DE/E
@ 12.7 KeV |
Focus
Spot Size m
HWHH |
End Station Identifier |
Flux (focused) @ 12 KeV Phot/mm2/sec |
| I I |
|
5 – 25 |
1 x 10-4 |
100 x100 |
ID-C |
1014 |
| II III |
D.S. ID |
12.66 OR 14.78 |
2 x 10-4 |
100 x 100 |
ID-E |
1014 |
| III IV |
BM |
6 – 17 |
2 x 10-4 |
500 x 500 |
BM-B |
1011 |
| IV II |
D.S. ID |
9 – 17 |
2 x 10-4 |
100 x100 |
ID-D |
1014 |
Key:
D.S.
ID: Downstream undulator
BM: Bending
magnet
Figure
1.1 shows a schematic of the optical trains for the 3 sector 24 insertion
device beamlines, indicating the positions of all
main optical elements. The following
list details the overall performance goals for all 4 sector 24 beamlines:
1) Phase I: “Pass-Through” Undulator
Beamline. The first beamline
developed (using the upstream, outboard-projecting undulator)
will consist of a single optical train, supplying a single experimental endstation with doubly focused monochromatic light from 5
to 25 KeV, with a nominal band pass of order 10-4
(DE/E). Monochromitization
will be accomplished by a cryogenically-cooled double crystal Silicon Bragg
monochromator. A Kirkpatrick-Baez
(K-B) mirror pair will focus the monochromatic beam.
2) Phase II: “Single-Crystal Side-Bounce Undulator
Beamline. A single,side-bounce cryogenically-cooled 220 silicon monochromator will accept the residual beam from a diamond-transmission
monochromator using beam from the downstream, inwardly projecting
undulator (see Phase IV, below). The side-bounce
mono will deliver a monochromatic beam near 12.6 KeV,
with a nominal take-off angle (2θ) of 29.54o from the centerline.
The 220 Si crystal
will be mounted on a cooling stage that incorporates a vertical translation.
A second silicon crystal (311-cut) will be mounted on this stage, with
independent roll and pitch fine adjustments such that a second energy (14.78
KeV) will be selectable by a vertical translation of the cooling
stage (following the same 29.54o take off angle provided by the
220 crystal). This beamline will also use K-B focusing.
3) Phase III: Bending Magnet Beamline. The fourth beamline
developed by NE-CAT will use the bending magnet port of the assigned sector.
The phase III beamline will incorporate a water-cooled
Si-111 monochromator with sagittal focusing, providing a spectral range from 5 to 17
KeV (2 eV bandpass).
Vertical focusing will be accomplished with a mechanically figured mirror.
4) Phase IV:
Tunable Large-Offset, Side-Bounce Undulator Beamline. A pair of beamlines
will be sourced by the downstream, inboad-projecting
undulator. Monochromatization and physical separation of the Phase I
and Phase III beamlines will be accomplished with
a large horizontal-offset (1.5m) diamond transmission monochromator,
with a spectral range between ~8.5
and17 keV. The
undiffracted radiation is passes on to the Phase
II Fixed-Energy Side-Bounce monochromator. As with Phases I and II, Phase III will use
K-B focusing.
This document presents a detailed preliminary design for Phases I and II only. Separate PDR’s for the proceeding phases will be submitted for review during the current calendar year. The Phase IV beamline will be developed during the first renewal phase of our NCRR funding. We do, however, present preliminary, overall hutch layout and conceptual beamline design “sketches” for the side station and bending magnet beamlines in the present document.
2. Changes Since Submission of Conceptual Design
Report.
Three major
changes in our optical design have occurred since submission of our Conceptual
Design Report in spring of 2002. None
of these changes have substantively altered the overall beamline
layout or long-term work plan. These changes are enumerated below:
1) We have reassigned the upstream and downstream undulators
to different beamlines. Originally, we had planned on sourcing the Phase
I undulator beamline with
the downstream, inwardly projecting undulator and
Phase II and IV (PDR teminlolgy) with the upstream
undulator. We
realized that it will be far easier to accommodate the Phase II and Phase
IV (PDR nomenclature) monochromators if they are
situated inboard of the Phase I beam. With
this reassignment of the undulators, the mechanical
mounts and cooling systems for Phase II and IV monochromator
elements will be oriented away from the Phase I (outboard) undulator
beam, minimizing stearic clash between Phases I,
II and IV. The only significant effect
of this design change is in the placement of the penetrations in the first
and secondary optics enclosures.
2) In our CDR we planned on using diamond-based monochromators
in all NE-CAT insertion device beamlines. A patent encroachment suit has been filed by
General Electric Corporation against the one commercial diamond vendor capable
of sourcing diamonds of the requisite optical quality and size (
3) An additional tungsten bremsstrahlung collimator (located in the FOE) has been added
to simplify the horizontal shielding plan.
4) The length of 24-ID-B has been reduced by 10” on the upstream side to increase the width of the secondary egress path between 24-ID-B and 24-ID-D.
3. Beamline Technical Specifications.
All
four sector 24 NE-CAT beamlines are single-purpose,
fixed configuration macromolecular crystallography beamlines. The following functional elements must be provided by the various beamline subsystems:
· Shielding and safety systems must include enclosures for the optics and
the experimental hardware and be capable of protecting personnel from radiation
and equipment from such faults as loss of power, cooling fluid, etc.
· Optics systems must be capable of delivering a focused monochromatic beam
with long-term positional stability to a sample 40-60 meters from the radiation
source. The required positional stability
region (horizontal and vertical) is a square of edge length 10 microns with
a characteristic time measured in hours.
· Beam transport systems must convey the beam from the sector front end to
the sample position via ultra high vacuum paths to minimize intensity loss
(due to absorption) and scattering background.
· Utility systems must provide conventional infrastructure such as plumbing
of water and compressed gases; electrical power; HVAC capability; liquid nitrogen;
and mechanical support.
· Control systems must provide interactive (and secure) local and remote
control of all optics, sample handling and detection subsystems.
· Front ends, insertion devices and dipole magnet must provide an X-ray beam
with an energy range of at least ~5KeV to ~30 KeV.
· The lab and office module must provide for mechanical equipment setup and
maintenance; wet laboratory capability for sample preparation; and office
space for operations staff and data reduction.
The required performance
characteristics for the four NE-CAT sector 24 beamlines
are:
3.1 Phase
I “passthrough” beamline,
using outboard-projecting undulator:
·
An energy range of 5-25keV.
·
An unfocused beam of approximately 1012 X-rays/mm2/sec
to a sample about 65 meters from the source.
·
A focused beam of approximately 1014 X-rays/mm2/sec
to a sample about 65 meters from the source.
·
A focal spot size using mirrors of <100 μm horizontal by <100
μm vertical.
·
A beam with an energy bandwidth of ΔE/E ~1 x 10-4 at an energy of ~12.66
keV.
·
A beam that is stable to <10% of its size (e.g., a 100 μm beam will have a positional
stability of 10 μm).
3.2 Phase II single-crystal
side-bounce beamline using the inboard-projecting
undulator:
·
A fixed energy at
~12.66KeV or 14.78 KeV,
with a fixed take-off angle (2θ) of 29.54o.
·
An unfocused beam of approximately 1012 X-rays/mm2/sec
to a sample at 58 meters from the source.
·
A focused beam of approximately 1014 X-rays/mm2/sec
to a sample at 58 meters from the source.
·
A focal spot size using mirrors of <100 μm horizontal by <100
μm vertical.
·
A beam with an energy bandwidth of ΔE/E <2 x 10-4 at an energy of
~12.66 keV.
·
A beam that is stable to <10% of its size (e.g., a 100 μm beam will have a positional
stability of 10 μm).
3.4 Phase III bending magnet
beamline:
·
An energy range of ~5-17keV.
·
An unfocused beam of approximately 1010 X-rays/mm2/sec
to a sample about 35 meters from the source.
·
A focused beam of approximately 1011 X-rays/mm2/sec
to a sample about 35 meters from the source.
·
A focal spot size (using either zone plates or mirrors) of <500 μm horizontal by <300 μm vertical.
·
A beam with an energy bandwidth of ΔE/E <4 x 10-4 at an energy of
~12 keV.
·
A beam that is stable to <10% of its size (e.g., a 500 μm beam will have a positional
stability of 50 μm).
3.5 Phase IV diamond-transmission
beamline, using the inboard-projecting undulator:
·
An energy range of ~8.5-17keV.
·
Horizontal offset of monochromatized beam by
1.5 m.
·
An unfocused beam of approximately 1012 X-rays/mm2/sec
to a sample about 42 meters from the source.
·
A focused beam of approximately 1014 X-rays/mm2/sec
to a sample about 42 meters from the source.
·
A focal spot size using mirrors of <100 μm horizontal by <100
μm vertical.
·
A beam with an energy bandwidth of ΔE/E <2 x 10-4 at an energy of
~12.66 keV.
·
A beam that is stable to <10% of its size (e.g., a 100 μm beam will have a positional
stability of 10 μm).
3.6 End Stations
The sector 24 endstations will incorporate similar
designs and subsystems used in the NE-CAT 8BM endstation. The principal components of all four endstations are:
·
Collimation system, consisting of two independent arrays of pairs of vertical
and horizontal slit blade pairs, separated by ~ 1 m. Individual slit blade positions WILL have a
reproducibility of ~ 5μ and operate in roughing
vacuum to minimize air scatter and beam intensity degradation via absorption.
·
Fast monochromatic beam shutter with opening and closing times less than 20
msec, synchronized with the motion state of the
crystallographic spindle.
·
Precision crystallographic goniometer (using
the Kappa geometry), with remotely controlled X,Y
and Z spindle adjustments. The radius
of the sphere of confusion of the crystallographic axis will be less than
20μ. The
minimum stepping unit of the crystallographic scanning axis must be less than
1.75 x 10-5 rad. Maximum stepping rate
must be greater than 10o/sec to efficienty
support “Friedel Flipping” (inverse beam) data collection.
·
·
Ionization and sample fluorescence monitors.
·
Precision, remotely steered miniature beam stop.
·
Video microscope capable of visualizing crystals with edge lenths <10μ.
·
Multi-element fast CCD and detector positioner:
1. active area consisting
of at least 4000 x 4000 pixel elements with an effective pixel size less than
100x100 μ.
Phase I:
ADSC Q315: 6000x6000 pixels (315x315 mm active area)
Phase II,III: ADSC Q210
Phase IV:
ADSC Q315
2. aggregate
CCD array readout times less than 2 sec with high sensitivity and low noise.
3. maximum
spindle to detector distance (SDD)> 1m, minimum SDD < 0.1 m, with ability
to pitch detector about the 2θ axis (LR Desing A-frame).
·
High performance data flow and computational cluster.
This section describes mechanical and optical components of the Phase I and II sector 24 ID beamlines