status of target design

Status of Target Design

Chris Booth

Sheffield

28th October 2004

Chris Booth University of Sheffield 2

Outline• Specifications

• Diaphragm Spring suspension

• Linear Drive

– First prototype

– New design

• Plans

Chris Booth University of Sheffield 3

Draft Specification• Transit: 40 mm

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

Chris Booth University of Sheffield 4

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

Chris Booth University of Sheffield 5

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

Chris Booth University of Sheffield 6

Specs Continued• Must operate in vacuum and radiation

environment

• Must not interfere with ISIS operation!!

Chris Booth University of Sheffield 7

Diaphragm spring

Target

Array of coils Magnet(s)

Position measurement

Schematic design

Linear Drive

Chris Booth University of Sheffield 8

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

Chris Booth University of Sheffield 9

Diaphragm Spring

Chris Booth University of Sheffield 10

Linear Drive (1)• Tests with first prototype

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

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Chris Booth University of Sheffield 12

Armature

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Armature

S N N S

Chris Booth University of Sheffield 14

Armature

S N N S

~ radial field

Chris Booth University of Sheffield 15

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

Chris Booth University of Sheffield 16

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

Chris Booth University of Sheffield 17

Improved armature design

soft iron Nd-Fe-B magnets

Sectored magnets – fixed together with aircraft glue

Chris Booth University of Sheffield 18

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?

Chris Booth University of Sheffield 19

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

Chris Booth University of Sheffield 20

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