evolution of the detector module design for corelli at sns ·...
TRANSCRIPT
Evolution of the Detector Module Design for CORELLI at SNS
2 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Outline of Talk
• Introduc)on to Corelli and Corelli Detectors • Why the Need for a Different Detector Design • Design Challenges • Working Solu)ons • Final Comments
3 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
What is CORELLI? aka Elastic Diffuse Scattering Spectrometer (managed as part of the SING II project)
Corelli is a sta)s)cal chopper spectrometer designed and op)mized to probe local disorder through diffuse sca@ering from single crystals It combines the high efficiency of white beam Laue diffrac)on with energy discrimina)on by modula)ng the beam with a sta)s)cal ‘correla)on’ chopper Corelli will be the first instrument in the world dedicated to the study of diffuse sca@ering with energy discrimina)on
4 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
CORELLI is located on BL9 at SNS
Corelli BL9
Proton Beam Direc2on
Bridge to CLO
5 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Instrument Layout
20 m
2.5 m
Moderator C/L Sample C/L Detector C/L
Choppers
Sample Scattering Vessel
6 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Detector Array
• 3 rows of He-‐3 Filled Linear Posi)on Sensi)ve Detectors (GE Reuter-‐Stokes) • 1.27 cm diameter x 83.9 cm ac)ve length, Spa)al Resolu)on ≈ 1 cm x 1 cm • 16 tubes per module, 30 modules per row for a total of 1440 tubes • Ver)cal Range -‐ 28.5o to + 28.5o • Horizontal Range -‐ 23o to + 152o
• Ini)al phase to consist of 38 modules, mostly located along middle row
Sample Scattering Vessel Detector Array Frame
7 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
No Isolation Valve for Corelli …
• No room to fit valve to isolate sample vacuum space from detector vacuum space
• Thus, we need to vent and pump en2re vacuum vessel with each sample change
8 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
... Resulting in a Few Design Challenges Compared with the ‘ARCS’ detector 1. To reduce pump down )me,
detector electronics need to be placed inside compartment which is separate from the vacuum space
ARCS design open to vacuum
2. 15 Wa@s per module
twice that of ARCS 8-‐pack design
3. Electronic circuit board designs (preamplifiers in par)cular) require temperatures to be stable to within 1-‐2 oC for reliable performance
same as for ARCS but harder to achieve for Corelli due to periodic vent/vacuum cycles ARCS 8-‐pack detector module
2.54 cm dia. x 100 cm long tubes
9 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Design Challenge #1 Met
Electronics Tray Fits in Compartment Behind
Detector Tubes
Detector Electronics Tray Assembly
10 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Design Challenge #2 (15 Watts of Power) Two Options Considered:
• Ac)ve Cooling (forced air flow through electronics compartment)
• Passive Cooling via heat sinks and black surfaces
Cooling Lines
Painted Black Inside and Out
11 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Thermal Imaging Identified ‘Hot Spots’ for Placement of Heat Sinks
12 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Custom Vacuum Chamber Built to Simulate Vent/Vacuum Cycles in Lab • Atm to <1E-‐4 Torr in 30 min
• Cooling lines connected to house air (and flow controllers)
• Circuit boards have built in thermal sensors
• Also used TC gauges to measure surface temperatures
• Power and signal cables to quan)fy stability of detector electronics
13 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Design Challenge #2 Met
• We targeted < 60 oC to be consistent with ARCS design
• Able to adequately cool with reasonable air flow (0.5 CFM)
• Also able to passively cool with black surfaces, modest reposi)oning of boards, and applica)on of heat sinks
0
10
20
30
40
50
60
0 20 40 60 80 100 120
Tempe
rature oC
Time in hours
0
10
20
30
40
50
60
0 20 40 60 80 100 120
Tempe
rature
o C
Time in hours
14 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Design Challenge #3 (temperature instability of preamps)
• Temperature stability during 2 hour vent cycle was not achieved
• Instrument team needs to be able to take data once acceptable vacuum is reached (est. 2-‐3 hours)
• Time constant to return to equilibrium temperatures > 24 hours
45 46 47 48 49 50 51 52 53 54
0 2 4 6 Tempe
rature oC
Time in Hours
Repump Begins
Vent Begins
15 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Effect of Temperature Drift on Calculated Neutron Position
• Temperature drii of preamps is known to have detrimental effect on calculated event posi)on
• Effect much more pronounced near tube ends than center
0
10
20
30
40
50
60
70
46 48 50 52 54 56 58 Ch
ange in Peak Po
si2o
n (m
m)
Temperature (oC)
tube center tube end
16 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Design Challenge #3 Met with Electronic Solution
Preamplifier modifica)on provides solu)on to peak shii problem
capaci?ve decoupling of
1st stage op amp leads to
excep?onal peak stability
with temperature change -‐10 -‐8 -‐6 -‐4 -‐2 0 2 4 6 8
10
46 48 50 52 54 56 58 Ch
ange in Peak Po
si2o
n (m
m)
Temperature (oC)
tube center tube end
17 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Performance Stable Over Temperature Range Expected During Sample Change-Out
units RED (mm)
GREEN (mm)
BLUE (oC)
-‐10
-‐9
-‐8
-‐7
-‐6
-‐5
-‐4
-‐3
-‐2
-‐1
0
1
2
3
4
5
0 1 2 3 4 5 6 7 8
Time AAer 2 Hour Vent to Atmosphere (hours)
Change in Peak Posi)on (mm)
Change in Board Temperature Aier Vent (oC)
Change in FWHM (mm) Vent Begins
Repump Begins
18 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Redesign of Preamplifier Boards
• Incorporated decoupling capacitor modifica)on • Improved protec)on circuitry to buffer against HV breakdown (Corona)
• Plug-‐in connectors to facilitate tray removal for maintenance
19 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Upon further testing, vacuum group recommended removing all cabling from vacuum space
Rear view of detector module showing NW25 bellows
20 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
The first phase of 38 Corelli detector modules are currently undergoing assembly and testing, on track for an early CD-4 finish date in Feb 2014
Preparing for Installation
21 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name
Detector Development Team – Key Players
• George Rennich Lead Engineer
• Bill Turner Designer
• Mark Wendel Thermal Analysis
• Kevin Berry, Jus)n Beal Detector Development
• Vlad Sedov Electronics Development
• Feng Ye Instrument Scien?st