Hardware Progress

Doug Abernathy

ARCS Instrument Scientist

ARCS IDT Meeting Lujan Center, LANL September 30, 2002

SNS Instrument Systems Argonne/Oak Ridge

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

SNS Instrument Systems Argonne/Oak Ridge

Shielding calculations

Concentrating on:

• Beamstop design

• Crosstalk between instruments

• Background due to proton transport line and choppers

SNS Instrument Systems Argonne/Oak Ridge

A brief report on the ARCS/MERLIN WorkshopDoug Abernathy

ARCS IDT Meeting Lujan Center, LANL September 30, 2002

SNS Instrument Systems Argonne/Oak Ridge

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

SNS Instrument Systems Argonne/Oak Ridge

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)

SNS Instrument Systems Argonne/Oak Ridge

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

SNS Instrument Systems Argonne/Oak Ridge

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)

SNS Instrument Systems Argonne/Oak Ridge

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

SNS Instrument Systems Argonne/Oak Ridge

Polarizing filters

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

Different conclusions:•None

Future actions:•Monitor filter performance in other instruments

SNS Instrument Systems Argonne/Oak Ridge

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

SNS Instrument Systems Argonne/Oak Ridge

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”

SNS Instrument Systems Argonne/Oak Ridge

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

SNS Instrument Systems Argonne/Oak Ridge

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