HYSPEC INSTRUMENT DESIGN OUTLINE

1

• HYSPEC INSTRUMENT DESIGN OUTLINE
• The two models considered for HYSPEC inside
  outside (Mark)
• A breakdown of the components of the two models
  (Mark)
• Estimates of the cost (Mark)
• COFFEE BREAK
• Simulating the two models (Vinita) - MCNP
  considerations for shielding drum T0 chopper
  - McStas flux at sample considerations
• Engineering the drum shield the detector
  vessel (Bill) - Available angular ranges
• Polarization analyzer system (Igor)

2
The Generic Layout of HYSPEC
3
Model one BL14B, 25m from moderator (inside hall)

• Straight guide 4cm(w) x 15cm(h)
• 4.5m sample to detector

4
Model two BL14B, 37m from moderator (outside
hall)

• Curved guide 4cm(w) x 15cm(h)
• 4.5m sample to detector
• (6m sample to detector)

5

• HYSPEC is a time of flight spectrometer
• Measure on a surface in (Q,E) space
• Interrogate (Q,E) space by moving the
  surface around
• Needs high intensity to sample many (Q,E)
  surfaces
• (160 detectors 20 x 8-pack of LPSDs)

6

• HYSPEC is -
• high intensity (hence focusing mono)
• medium resolution ?E/E 5
• thermal energy range
  5 lt E lt 100meV

G. Granroth D. Abernathy, ICANS-XVI
7
Resolution (qualitative not M.C.)
tM source (moderator) pulse width for EI ?tC
burst time for disk choppers
Primary spectrometer

• Low EI tM dominates
• High EI ?tC dominates

Secondary spectrometer
Spreading of pulse from chopper to sample
Secondary resolution governed by ratio of burst
time ?tC to distance LSD
8
Dashed lines Inside LMC25m, LCS2.45m,
LSD4.5m, ?tC50µs Solid lines Outside
LMC37m, LCS3.20m, LSD4.5m, ?tC50µs
9
OUTSIDE
INSIDE
Detector vessel
Sample stage floor
Drum shield
Focusing crystals(Focusing monochromator)
Counter rotating diskchoppers (T2)
Order suppressor chopper (T1b)
m3 guide
Frame overlap chopper (T1a)
T0 chopper
10

• T0 chopper
• Located just outside SNS biological shield at
  6.3m
• Remove (reduce) fast neutron (MeV, keV, eV)
  flux
• Horizontal axis rotors 20cm of Inconel running
  at 60 (or 30) Hz
• Inside 2 counter rotating choppers - Total
  of 40cm of Inconel - Straight view of
  moderator - Drum shield thickness
• Outside 1 chopper - Effect of curved guide
  - Out of line of sight - Drum shield
  material/size
• Both cases reduce nos. of windows - Would
  like (want) to integrate vacuum with guide
  frame overlap chopper

11

• Frame overlap chopper
• Just after the T0 chopper (both inside
  outside)
• Even _at_ 25m (inside) frame overlap on a
  cold source is a problem
• 60Hz disk chopper
• B-loaded so that we can remove hot as well
  as cold neutrons if required
• Integrated vacuum with guide T0 chopper
  (windowless)

12
Measuring in the same frame
Measuring in the next frame
13
m3 Guide
Inside straight guide Outside curve to get out
of line of sight followed by 4m
straight
14
OUTSIDE
INSIDE
Detector vessel
Sample stage floor
Drum shield
Focusing crystals(Focusing monochromator)
Counter rotating diskchoppers (T2)
Order suppressor chopper (T1b)
m3 guide
Frame overlap chopper (T1a)
T0 chopper
15
Counter-rotating disk choppers

• Disks at 300Hz (?TC50µs)
• Diameter 700mm
• Gd coated

• Want to integrate vacuum with guide
• Picture above has external motors
• Picture left has internal motors

16

• Order suppressor chopper
• Counter rotating disk chopper _at_ 300Hz
• Opens 5 times per frame
• Need to block 4 out of 5 pulses
• Order suppressor chopper _at_ 60Hz
• B-loaded disk chopper (as for frame overlap
  other SNS disk choppers)
• Integrated vacuum with guide other
  choppers (windowless)

Example Counter rotating pair _at_ 300Hz, LMC25m
17
Focusing (monochromator) crystals
Non-polarizing HOPG(002)
Polarizing Heusler(111)
Picture is of double focusing mono for MACS at
NIST
Picture is of double focusing Heusler mono
for IN20 at ILL
18
Monochromator drum shield

• Needs to stop the beam
• Inside direct view of source, needs to be
  more substantial. I.D. 0.4m, O.D. 2.8m
• Outside curved guide, out of line of
  sight, can be smaller. I.D. 0.6m, O.D.
  1.8M
• Using HFIR drum (see right) as a starting
  point.

19
OUTSIDE
INSIDE
Detector vessel
Sample stage floor
Drum shield
Focusing crystals(Focusing monochromator)
Counter rotating diskchoppers (T2)
Order suppressor chopper (T1b)
m3 guide
Frame overlap chopper (T1a)
T0 chopper
20
Relationship disk choppers drum shield

• Inside choppers must be inside drum shield
• Outside - drum shield is smaller
  (larger I.D., smaller O.D) - choppers can be
  further from sample for same
  resolution

21
(No Transcript)
22
OUTSIDE
INSIDE
Detector vessel
Sample stage floor
Drum shield
Focusing crystals(Focusing monochromator)
Counter rotating diskchoppers (T2)
Order suppressor chopper (T1b)
m3 guide
Frame overlap chopper (T1a)
T0 chopper
23
Fermi chopper high resolution mode
24
OUTSIDE
INSIDE
Detector vessel
Sample stage floor
Drum shield
Focusing crystals(Focusing monochromator)
Counter rotating diskchoppers (T2)
Order suppressor chopper (T1b)
m3 guide
Frame overlap chopper (T1a)
T0 chopper
25
Sample stage dance floor airpads

• Sample stage
• Dance floor (granite tiles)
• Airpads

Picture is IN20 triple axis spectrometer at the
ILL, Grenoble
26
Detector vessel
Angular range 60 (horz), 15 (vert)Sample
detector dist 4.5m, (6m) Detectors 20x 8-pack
LPSDs (1.2m long for LSD4.5m)
Copies of ARCS/SEQUOIA Atmosphe
re Argon (LPSDs wont work
in He) Electronics/DAE As per
ARCS/SEQUOIAFront window Permanent rough
collim inside the
detector Outside vessel Radial collimator
(remove SE scattering)
Polarization analyzers
27
(No Transcript)