Status of Target Design

Chris Booth

Sheffield

28th October 2004

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Outline• Specifications

• Diaphragm Spring suspension

• Linear Drive

– First prototype

– New design

• Plans

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Draft Specification• Transit: 40 mm

• Entry ≥ 5 mm into beam in ≤ 2 ms(see plot)

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Target edge trajectoryWith spring

45

50

55

60

65

70

75

80

0 5 10 15 20 25 30

t (ms)

Posi

tion

(mm

)

beam

target

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Draft Specification• Transit: 40 mm

• Entry ≥ 5 mm into beam in ≤ 2 ms(see plot)

• Cycle time: 20 ms

• Positioning accuracy: 0.5 mm

• Timing accuracy: ~ 0.2 ms

• Frequency: (baseline) 1 to 3 Hz on demand

• (optimal) 1 to 50 Hz

• Maximum proton rate: 1.41012 per second

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Specs Continued• Must operate in vacuum and radiation

environment

• Must not interfere with ISIS operation!!

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Diaphragm spring

Target

Array of coils Magnet(s)

Position measurement

Schematic design

Linear Drive

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Diaphragm Spring suspension• Frictionless “bearing” allowing vertical movement• Must keep armature on axis to 0.2 mm (for

magnet and position monitor)• Design of small spring obtained from Tom

Bradshaw (RAL)• Scaled up to allow ≥40 mm travel• Finite element studies to check stress and lifetime

issues (Lara Howlett)• Be-Cu sheet procured• Wire-erosion performed in Eng. Dept. workshop

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Diaphragm Spring

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Linear Drive (1)• Tests with first prototype

– Moving magnet shuttle (2 magnets)– Static single/double coil excitation– No commutator

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Armature

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Armature

S N N S

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Armature

S N N S

~ radial field

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x o o x o o

Coils

Armature

o x x o x x

x o o x o o

x o o x o o

Coils

Armature

o o x o o x

x x o x x o

“3-phase” drive

x o o x o o

Coils

Armature

x o x x o x

o x o o x o

x o o x o o

Coils

Armature

x o o x o o

o x x o x x

1 3

42

Magnetic actuator plus Hall switches bipolar drive

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However!• Current armature/coil design does not

give required acceleration– 280 N kg–1 at 20 A mm–2

– Need ~950 N kg–1

revised armature design current density 35 A mm–2 for short

pulses

• Effective cooling essential

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Improved armature design

soft iron Nd-Fe-B magnets

Sectored magnets – fixed together with aircraft glue

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Cooling• Coils potted in thermally conductive resin

• Water cooling circuit integrated into outer aluminium housing

– Resin inside vacuum housing?

• Coil temperature monitored with thermistors

• Possible to monitor magnet temperature too?

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Radiation concerns

• Wasn’t possible to make in situ

measurements this autumn

• Radiation levels may be radically different

without target in operation

• Studying documented radiation hardnesses

• Still hope to make measurements at ISIS in

spring

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Plans for next months• Complete revised design

– Optimised coil, armature design

– 3-phase switched drive circuit

• Currently mounting 1st prototype vertically on diaphragm springs– Measure lateral stability

– Debug position readout system, check read speed

– Develop cooling and temperature measuring system

• Switch to new drive as soon as available

• Develop control hardware & software