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January 25, 2005 GRETINA 2004 Review 1
GRETINA2004 Annual Review
Steve Virostek
Lawrence Berkeley National Lab
Mechanical System
January 25, 2005 GRETINA 2004 Review 2
Presentation Overview
• Mechanical system conceptual design
• Detector mechanical interface
• Installation site interfaces
• Mechanical requirements document
• LN system and target chamber
• Detector scanning table
• Prototype detector QC: CMM and X-ray
January 25, 2005 GRETINA 2004 Review 3
Mechanical Conceptual Design
January 25, 2005 GRETINA 2004 Review 4
D1
D2
R2
R1
S
Target Ball Radius
• Scientific considerations: the effect on the volume available within the ball and the efficiency of data capture
• Mechanical issues: the quarter sphere detector support radius and the position of the detector mounting flanges
Detector Modules Mounted in 2 Structure around Target Ball at Center
2Structure/Target Ball Size Parameters
January 25, 2005 GRETINA 2004 Review 5
GRETINA Assembly Features
Detector module Cap
Preamp housing LN dewar
Quarter sphere shell
Axle bearings
Axle
Worm and worm gear set
HexapodRailroad car, tracks
Flange
Wedge plate (under and attached to detector flange)
January 25, 2005 GRETINA 2004 Review 6
Quarter Sphere Structure• Large-radius quarter sphere allows space for
17 detector module flanges as well as sufficient material to provide a stiff structure for accurate positioning
• As the quarter sphere radius increases, the required thickness and weight increase as well – eventually reducing the clearance around GRETINA due to the larger support components
• Preliminary calculations indicate a shell thickness of 3 to 4” with a quarter sphere radius of 25 to 30”
January 25, 2005 GRETINA 2004 Review 7
Other Design TopicsAXLE
• Design issues include loaded quarter sphere weight and distances to the bearings
• A larger axle tube size reduces weight but increases the axle bearing cost and impinges on space constraints
• Preliminary calculations indicate an axle tube of 10” OD and 1/2 to 1” thick wall
HEXAPOD
• The hexapod (or Stewart platform) is a fairly standard octahedral mount using ALS struts
• The hexapod is very stiff due to the tensile/compressive (no bending) loading of the struts and is finely adjustable over a large range
• Alignment of a hexapod is non-intuitive, but is easily accomplished using a computer code
WEDGE PLATE
• The absolute error in the shape of the detector caps should be small
• In order to nest the detectors as closely as possible, the position of the caps must be controlled carefully with the flange mount
• Since the distance from the cap to flange is not small nor direct (tolerance stack-up), we will correct for the position of each flange with a custom made wedge plate
• Can accommodate errors of 3 mm in the flange plane, 5 mm out of plane and 1º tilt errors
January 25, 2005 GRETINA 2004 Review 8
Detector Mechanical Interface
Module Caps Nest Together with 1mm Nominal Gap
Quad Detector ModuleWedge Plate
2 Structure
+ +
January 25, 2005 GRETINA 2004 Review 9
Site Installation Overview
• TBD
January 25, 2005 GRETINA 2004 Review 10
ANL Installation
January 25, 2005 GRETINA 2004 Review 11
LBNL Installation
The 8x8 needs to move in so that its right end is at the centerline
January 25, 2005 GRETINA 2004 Review 12
MSU Installation
January 25, 2005 GRETINA 2004 Review 13
ORNL Installation
January 25, 2005 GRETINA 2004 Review 14
Requirements Document• Requirements are for the Mechanical System as defined in the PEP:
– Detector Support Structure– Liquid Nitrogen System (interface only)– Target Chamber (interface only)– Detector Installation Tool
• The LN system (ORNL) and the target chamber (Washington U.) design requirements will be presented in separate documents prepared by their respective developers
• Purpose of ME Requirements Document– Based on the Functional Requirements in the PEP
– Describes mechanical requirements necessary to meet Functional Requirements and physics goals
January 25, 2005 GRETINA 2004 Review 15
Requirements Document (details)
Coordinate Systems
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Tolerances
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•
January 25, 2005 GRETINA 2004 Review 16
Requirements Document (details)
2 Spherical Structure
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•
January 25, 2005 GRETINA 2004 Review 17
Requirements Document (details)
Structure and Tracks• • • • Translation and Rotation• • • •
January 25, 2005 GRETINA 2004 Review 18
Requirements Document (details)
Detector Installation Tool
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•
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Material Issues
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•
January 25, 2005 GRETINA 2004 Review 19
Requirements Document (details)
Interfaces
• Mechanical …
• Electrical …
• LN System
• Target Chamber
• Transportation
January 25, 2005 GRETINA 2004 Review 20
Requirements Document (details)
Interfaces
• Site Specific …
• Operating Envelope …
• Site Requirements …
January 25, 2005 GRETINA 2004 Review 21
LN System and Target Chamber
• TBD?
January 25, 2005 GRETINA 2004 Review 22
Detector Scanning TableCoincidence scan setup
Scanning table Adjunct cart
The scanning table may be used with or without the adjunct cart.
• Horizontal and vertical americium collimators outline surface areas of crystals
• Vertical cesium collimator…• Vertical cesium collimator in conjunction with slit collimators and cloverleaf detectors…
• Slit collimators with external source….
January 25, 2005 GRETINA 2004 Review 23
Scanning TableTriple-crystal prototype detector module
Cloverleaf detectors
XY drive for vertical collimator Elevation drive’s tracking rollers
Vertical source- collimator onXY drive
Horizontal source-collimator on Z drive
Detector module rotary table withdegree markings
Scan cart
Cloverleaf elevation drive
Adjunct cart
Horizontal slits collimator, attached to Z drive
January 25, 2005 GRETINA 2004 Review 24
Scanning Table DetailsTriple-crystal prototype detector module
Slit collimator, attached to Z axis
Cloverleaf detectors
Cloverleaf elevation drive
Americium or cesium vertical collimator
Horizontal americium collimator (not visible)on Z drive
Detector module rotary table withdegree markings
XY drive for vertical collimator Elevation drive’s tracking rollers
January 25, 2005 GRETINA 2004 Review 25
Detector CMM Measurement
366 points measured at room and liquid-nitrogen temperatures
Results:• Deviation from design value = 0.2 mm (RMS)• Warm – cold difference = 0.02 mm (RMS)
January 25, 2005 GRETINA 2004 Review 26
Detector X-ray Imaging• Crystal positions were determined by X-ray imaging
at the UC Berkeley Medical Center
The three crystals were positioned withan accuracy of better than 0.5 mm.