Hardware Progress Doug Abernathy ARCS Instrument Scientist ARCS IDT Meeting Lujan Center, LANL...

Hardware Progress

Doug Abernathy

ARCS Instrument Scientist

ARCS IDT Meeting Lujan Center, LANL September 30, 2002

SNS Instrument Systems Argonne/Oak Ridge


ARCS Test Chamber

• Detector Mounting Tests– Holds up to 16 tubes to test

Electronics in Vacuum Module Handling

• Vacuum Tests– “Crispy Mix” Mounting and

Vacuum Effects

– Installation Issues


Shielding calculations

Concentrating on:

• Beamstop design

• Crosstalk between instruments

• Background due to proton transport line and choppers


A brief report on the ARCS/MERLIN WorkshopDoug Abernathy

ARCS IDT Meeting Lujan Center, LANL September 30, 2002


Agenda:Thursday 9/26/02 ISISMorning: Introductions and instrument conceptsAfternoon: Primary spectrometer Moderator; guides; choppers; polarizing filters; tourFriday 9/27/02 Morning: Secondary spectrometerTank; detectors; shielding; beamstop; sample environment & manipulation; softwareAfternoon: General discussion and future plans


MERLIN concept

Original-High count rate, medium resolution chopper spectrometer as an upgrade to HET; complementary to MAPS; designed with guides and radial collimator

Sample-detector distance = 2.5mModerator-sample distance = 13.8mAngular coverage = steradiansModerator: ambient water N9 (HET position)

New ideas-Moderator: ambient water S4 (blocks S5), choice of poison depthModerator-sample distance = 11.6mDetectors: cylindrical array of 3m long LPSDs (no Al windows)Choppers: Gd based Fermi (needs disk chopper to stop >200meV neutrons)


Moderator

Similar conclusions:•Use ambient water•Poison depths should be increased to >20mm but not eliminated due to large tails

Different conclusions:•None

Future actions:•Exchange source files for modeling•ARCS – model performance for ARCS and SEQUOIA to determine final poison depth


Guides

Similar conclusions:•Taper guides continuously from source to sample (no nose section)•Use adjustable apertures and Soller collimators•Guide in shutter

Different conclusions:•MERLIN - use only m=3 guide; sollers on movable stage between T0 and Fermi choppers; use guide after Fermi chopper

Future actions:•MERLIN – test guide glass in HET; Soller with guide•ARCS – continue modeling (compare m values; guide just before sample; how apertures, Sollers and guide work together)


Choppers

Similar conclusions:•May need disk chopper•Need higher speed T0 chopper

Different conclusions:•MERLIN – disk chopper for Gd based Fermi chopper•ARCS – disk chopper for multiple pulse and background suppression; vertical axis T0 chopper could combine disk and standard T0 chopper functions

Future actions:•MERLIN – test Gd slit package; continue development of 100Hz T0•ARCS – preliminary neutronic and engineering design of vertical axis T0; decide which type of T0 to pursue


Polarizing filters

Similar conclusions:•Leave position in beamline for future development of filters

Different conclusions:•None

Future actions:•Monitor filter performance in other instruments


Tank/detectors

Similar conclusions:•Get rid of large Al windows•Avoid shadowing of all pixels in detector arrayDifferent conclusions:•MERLIN – Use cylinderical array of 3m long tubes sealed at each end; 4x8 detectors mounted on a panel; tank is designed so that panels are necessary supports; use relatively short baffles that take the equivalent of one tube (~0.5m)•ARCS – Put electronics in vacuum along with detectors; minimal tank feedthroughs; use a gate valve to isolate sample area for changeoutFuture actions:•MERLIN – tests of long tubes in MAPS; vacuum tests of seals•ARCS – detector module tests in vacuum; continue design work on gate valve and sample manipulation


Shielding/beamstop

Similar conclusions:•Try to use standards

Different conclusions:•MERLIN – Standard ISIS shielding OK•ARCS – No true standards for SNS; need to use non-flammable materials or encapsulation

Future actions:•MERLIN – provide results of dose rate vs He detector measurements•ARCS – continue shielding calculations and determination of best alternative shielding materials; pursue Teflon binder for “crispy mix”


Sample environment & manipulation

Similar conclusions:•Need single crystal manipulation capability•Need easy and fast changeout of samples

Different conclusions:•MERLIN – pursue manipulation inside sample environment; use top loading CCR with rotation•ARCS – pursue design of spectrometer mounted manipulation

Future actions:•MERLIN – sample manipulation stage development program for MARI and MAPS•ARCS – continue to explore design of both types; build prototype for sample environment to test on PHAROS


Software

Similar conclusions:•Need better software to handle current and future data•Need standards for data files that cross all facilities

Different conclusions:•MERLIN – use Matlab and Fortran because of current expertise; involved in grid based computing initiative in the UK•ARCS – use Python and C++

Future actions:•Common ground should be explored and at the minimum standards for data storage and instrument description need to be adopted

Hardware Progress Doug Abernathy ARCS Instrument Scientist ARCS IDT Meeting Lujan Center, LANL...

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