Hall A Tungsten Calorimeter

1
Hall A Tungsten Calorimeter

• Preliminary Mechanical Design
• and
• Thermal Analysis
• May 14, 2004

2
Contents

• Objective Requirements
• Location
• Mechanical Design
• Thermal Analysis
• Silver/Tungsten Comparisons
• Assembly, Test Installation
• Cost Estimate
• Schedule
• Open Questions

3
Objective Requirements

• OBJECTIVE
• Produce a calorimeter for beam current
  measurements in Hall A that meets or exceeds
  design specifications on schedule and within
  budget
• REQUIREMENTS
• Design must
• minimize heat leaks
• support thermometry
• contain heater(s) for calibration
• have method of cooling for repeat measurements
• be insertable due to invasive nature of
  calorimetric measurement
• fit in available Hall A beamline real estate
• survive in high radiation environment

4
Location

• Hall A Layout

• Super Harp Girder
• - Locate Calorimeter between BCMs on girder

5
Mechanical Design
Hall A Beamline 1.5 Dia

• Real Estate Constraints
• Plenty of room above the girder
• Primarily constrained by distance from beamline
  to girder

Super harp girder cross-section
6
Mechanical Design

• The Slug

BEAM
Volume 3131.32 cm3
7
Mechanical Design

• The Slug (Cont)

• Desire a fully dense, machinable part with good
  thermal properties
• Pure tungsten shapes typically produced by powder
  met process (pressing and sintering followed by a
  extrusion or swaging operation to reduce
  porosity). Subsequent operations to reduce
  porosity are not practical for a part a large as
  ours.
• Density and machinability can be improved by
  adding small amounts of Ni and Cu (W,Ni,Cu
  953.51.5) but thermal properties are less
  desirable.
• OSRAM/Sylvania produces a W,Cu 955 powder that
  will produce a very dense(99), homogenous,
  machinable part that has higher thermal
  conductivity than the above materials and still
  retains a high density. This is a unique process
  for making WCu composites that does not require
  infiltrating the Cu into a tungsten framework.
  Infiltrating would not be an option for a part as
  large as ours. This is the material of choice
  and has been used for the thermal analyses
  presented here.
• Thermal properties detailed later in the
  thermal analysis section

8
Mechanical Design

• Three Position Actuation Scheme
• Advances in compliant thermal interfaces that
  improve contact conductance in vacuum at low
  contact pressures offer an opportunity to cool
  the slug by conduction rather than convection.
  The scheme proposed eliminates the need to embed
  or otherwise attach cooling tubes that could
  increase the heat loss from the slug and would
  complicate the thermal response due to
  non-homogeneous diffusion properties.
• The three positions
• 1. Charging
• 2. Equilibrating
• 3. Cooling

9
Mechanical Design
10
Mechanical Design

• Mechanism

3 Position Pneumatic Cylinder
Turnbuckle
Ball Bushing
Instrumentation Power Feedthrus
Guided Support Feedthru Cross
Welded Bellows
Support Guide Rod
Slug Vertical Support Tube
11
Mechanical Design

• Slug Support Cooling Plate

Coupling to attach to vertical support tube
Oversized ebeam/ horizontal support tube allows
beam ops to continue when slug is equilibrating
or cooling (i.e., position 2 or 3)
Opening in base of tube to route wires to slug
Slug support arms
Socket set screws to support align slug
(contains ceramic insert to provide thermal and
electrical isolation)
Cu Cooling plate covered with compliant thermal
interface material
Cooling plate thermal isolation
Cooling plate alignment base
3 point mount to base of vessel to align cooling
plate to slug flat
12
Mechanical Design

• Compliant Thermal Interface

• SLIDE UNDER CONSTRUCTION!!

13
Mechanical Design

• Vacuum Vessel

Ø 16.5 CF
Ø 2.75 CF beamline port
Ø 8 CF access port
Ø 2.75 CF Chill water feedthru (jacketed to
minimize heat transfer to vessel)
Ø 4.5 CF port for instrumentation feedthru
3 point mount to super harp girder
Vessel baseplate
Ø 10 CF port provides access to cooling plate
14
Mechanical Design

• Calorimeter on super harp girder looking downbeam

15
Mechanical Design

• Calorimeter on super harp girder

Beam
16
Thermal Analysis

• Design Considerations
• Heat Loads
• Power IE lt 5kW
• Need to understand
• Thermal Response Time
• Heat Leaks
• Conductive through mounts and wires (TCs,
  Faraday, and heater(s))
• Radiation exchange with surroundings
• Cooldown Time
• Require ability to repeat measurements in 30
  minutes
• Effect of heater(s) on the thermal response of
  the device
• Correlate calibration vs. ebeam run

17
Thermal Analysis

• Thermal Modeling
• For initial modeling, a 2d transient
  axis-symmetric implicit finite difference (FD)
  model was written using Visual Basic for
  Applications in Excel
• Lumped mass model used for initial cooldown
  estimates
• IDEAS TMG transient solver now available at Jlab
  was used to check results from FD code and
  conduct more detailed analyses that more
  accurately capture the transient heat flow out of
  (and into) the slug. Future refinements will
  include radiation exchange and a heater model for
  comparisons between simulated calibration and
  ebeam runs. Analyses presented here use the FD
  code to capture the radiation losses.

18
Thermal Analysis

• Material Properties

• This slide under construction!!!

19
Thermal Analysis

• Finite Difference Thermal Model

• Decreased radius to match volume of actual slug
  to account for flat and entrance hole
• Conduction losses calculated at each time step.
  Heat flow based on assumption that T is linear
  thru the mounts.
• Radiation losses assume a two surface enclosure
  for each face of the slug (e.g., slug upbeam face
  only views Area1 of idealized chamber)

20
Thermal Analysis

• Finite Difference Thermal Model Input Panel

Kmount very small here to capture only rad
losses
21
Thermal Analysis

• IDEAS/TMG Model
• Took advantage of symmetry and modeled only half
  of the slug
• Mounting pins and wires modeled using beam
  elements
• Slug modeled using solid elements
• Wires are 8Lg, mounts are 1Lg

Downbeam TC Wires (spaced 120 apart)
Downbeam Mounting Pins (spaced 90 apart)
Faraday Wire
Upbeam TC Wires (spaced 120 apart)
Upbeam Mounting Pins (spaced 90 apart)
22
Thermal Analysis

• Initial and boundary conditions used for the
  simulations presented in the next several slides
• Uniform initial temperature distribution of 0C
• The ends of the wires and mounts are fixed at 0C
• From time t0s to t48s 5kW of beam power is
  deposited uniformly in a cylindrical volume 5mm
  in diameter that begins one radiation length into
  the slug at the base of the entrance hole and
  extends five radiation lengths into the slug
• At t350s the slug is brought in contact with the
  cooling plate. Overall contact conductance of
  1250W/m2/K to a fixed -15C (corresponds to a
  chill water temp of 12C)
• At t1050s the slug is lifted from the cooling
  plate

23
Thermal Analysis

• IDEAS/TMG Thermal Model Results

Beam off (t48s)
Measurement over/ begin cooldown (t350s)
Lift off cooling plate (t1050s)
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Thermal Analysis

• IDEAS/TMG Thermal Model Results

25
Thermal Analysis

• IDEAS/TMG Thermal Model Results

26
Thermal Analysis

• IDEAS/TMG Thermal Model Results

27
Thermal Analysis

• IDEAS/TMG Thermal Model Results

28
Thermal Analysis

• Finite Difference Thermal Model Results

29
Thermal Analysis

• IDEAS/TMG Finite Difference Thermal Model
  Results

30
Thermal Analysis

• IDEAS/TMG Finite Difference Thermal Model
  Results

31
Thermal Analysis

• IDEAS/TMG Thermal Model Results Summary

• This slide under construction!!!

32
Silver/Tungsten Comparisons

• This slide under construction!!!

33
Assembly, Test Installation

• This slide under construction!!!

34
Cost Estimate

• MECHANICAL Portion of Device
• Mechanism..10k
• Slug....9.5k
• Cooling Plate..5.6k
• Vacuum Vessel..................11.3k
• Chiller....6.7k
• TOTAL 43.1k

35
Schedule
36
Open Questions

• This slide under construction!!!