Innovative Magnet Development and Application at the National - - PowerPoint PPT Presentation

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Innovative Magnet Development and Application at the National - - PowerPoint PPT Presentation

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Innovative Magnet Development and Application at the National Synchrotron Light Source Eric B. Blum presented at Jefferson Lab February 20, 2002 Brookhaven Science Associates U.S. Department of Energy Acknowledgements Acknowledgements

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Brookhaven Science Associates U.S. Department of Energy

Innovative Magnet Development and Application at the National Synchrotron Light Source Eric B. Blum

presented at

Jefferson Lab February 20, 2002

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Brookhaven Science Associates U.S. Department of Energy

Acknowledgements Acknowledgements

George Rakowsky Don Lynch Sam Krinsky Klaus Halbach

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Topics Topics

Intro to NSLS Permanent Magnet Assisted Sextupole Superconducting Wiggler Hybrid In-Vacuum Undulator

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NSLS Facility NSLS Facility

Linac 120 MeV Booster Synchrotron 750 MeV X-Ray Storage Ring 2.8 GeV VUV Storage Ring 800 MeV

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Brookhaven Science Associates U.S. Department of Energy

Linac Linac

120 MeV 3 2856 MHz Sections:

  • 1- 5 m Varian
  • 2- 3 m SLAC

2856 MHz prebuncher Triode Electron Gun:

  • 1.5 A
  • 4.5 nsec pulse
  • 7 pulses, 92 nS apart
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Brookhaven Science Associates U.S. Department of Energy

Booster Booster

  • 120-750 MeV
  • 28.35 m Circumference
  • 4 Superperiods

2 Combined Function Dipoles (1.2 T) 2 Quadrupoles 1 Sextupole

  • 1.91 m Bending Radius
  • Nominal Tunes:

νx = 2.42 νy = 1.37

  • 52.886 MHz RF Frequency
  • 15 mA Beam Current
  • 0.87 Sec cycle
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Brookhaven Science Associates U.S. Department of Energy

Booster Photo Booster Photo

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Brookhaven Science Associates U.S. Department of Energy

VUV Storage Ring VUV Storage Ring

  • Operating Energy

0.808 GeV

  • Injection Energy

0.750 GeV

  • Peak Current

1.0 amp

  • Circumference

51.0 meters

  • Number of Beam Ports on Dipoles 18
  • Number of Insertion Devices

2

  • Max. Length of I.D.

~ 2.25 meters

  • Dipole Field

1.41 Tesla

  • Lifetime @ 200 mA

590 min

  • Lattice Structure(Chasman-Green)

Separated Function, Quad Doublets

  • Number of Superperiods

4

  • Magnet Complement
  • 8 Bending (1.5 meters each)
  • 24 Quadrupole (0.3 meters each)
  • 12 Sextupole (0.2 meters each)
  • Nom. Tunes (x , y)

3.14, 1.26

  • RF Frequency

52.886 MHz

  • Radiated Power

20.4 kW/A

  • RF Peak Voltage

80 KV

  • Design RF Power

50 KW

  • 4th Harmonic RF System
  • Synchrotron Tune

0.0018

  • Bunch Length (2σ)

9.7 cm (36 cm with 4th harmonic system)

  • RF Harmonic

9

  • Typical Number of Bunches

7

  • H Emittance

1.62 x 10-7 m-rad

  • V Emittance

3.5 x 10-10 m-rad

  • Power per Horizontal Milliradian

(1A) 3.2 Watts

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Brookhaven Science Associates U.S. Department of Energy

VUV Photo VUV Photo

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Brookhaven Science Associates U.S. Department of Energy

X-Ray Storage Ring X-Ray Storage Ring

  • Operating Energy

2.800 GeV

  • Injection Energy

0.750 GeV

  • Peak Current

350 mA

  • Circumference

170.1 meters

  • Number of Beam Ports on Dipoles30
  • Number of Insertion Devices

5

  • Max. Length of I.D.

~ 4.5 meters

  • Dipole Field

1.36 Tesla

  • Touschek Lifetime (250 mA)

>22 hr

  • Lattice Structure(Chasman-Green)

Separated Function, Quad Triplets

  • Number of Superperiods

8

  • Magnet Complement
  • 16 Bending (2.7 meters each)
  • 40 Quadrupoles (0.45 meters each)
  • 16 Quadrupoles (0.80 meters each)
  • 32 Sextupole (0.2 meters each)
  • Nom. Tunes (x , y)

3.8, 5.7

  • RF Frequency

52.886 MHz

  • Radiated Power 198 kW (0.25A)
  • RF Peak Voltage

1120 KV

  • Design RF Power

450 KW

  • Synchrotron Tune

0.003

  • Bunch Length (2s)

10.5 cm

  • RF Harmonic

30

  • Typical Number of Bunches

25

  • H Emittance

4.6 x 10 -8 m-rad

  • V Emittance

7.8 x 10 -11 m-rad

  • Power per Horizontal Milliradian

(250 mA) 32 Watts

  • Critical Energy

7.1 KeV

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Brookhaven Science Associates U.S. Department of Energy

X-Ray Photo X-Ray Photo

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Brookhaven Science Associates U.S. Department of Energy

Permanent Magnet Enhanced Sextupole Permanent Magnet Enhanced Sextupole

Motivation

  • X-Ray Ring low emittance lattice
  • Stronger sextupoles required
  • Existing sextupoles highly saturated
  • Sextupoles designed for 1/2 current required
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Brookhaven Science Associates U.S. Department of Energy

X-Ray Ring Lattices X-Ray Ring Lattices

Original Lattice

  • εx = 90 nm-rad
  • εy = 0.1 nm-rad
  • νx = 9.14
  • νy = 6.20
  • η = 0 in long straights

Low Emittance Lattice

  • εx = 46 nm-rad
  • εy = 0.08 nm-rad
  • νx = 9.83
  • νy = 5.71
  • η > 0 in long straights
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Brookhaven Science Associates U.S. Department of Energy

Lattice Plots Lattice Plots

High Emittance Lattice Low Emittance Lattice

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Brookhaven Science Associates U.S. Department of Energy

Sextupole Effectiveness Sextupole Effectiveness

Sextupole contribution ∝ β(s)M(s)η(s) βy(s) nearly unchanged at sextupoles η(s) smaller in low emittance lattice M(s) must be bigger

BUT

At 800 A (maximum sextupole current)

can only get chromaticity = 0

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Alternatives Alternatives

Increase current

  • Already running at over twice design current

Replace sextupoles

  • Expensive

Modify sextupoles

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Brookhaven Science Associates U.S. Department of Energy

P M Enhanced Electromagnet P M Enhanced Electromagnet

Proposed by Halbach, Proc. 7th FEL Conf. (1985) Excitation of pole comes from electromagnet coil Permanent magnet cancels flux in iron

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Sextupole Sextupole

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Brookhaven Science Associates U.S. Department of Energy

Sextupole Parameters Sextupole Parameters

Aperture Radius

5 cm

Magnetic Length

20 cm

Turns Per Pole

18

Maximum Current

800 A

Pole Tip Field (800 A)

0.65 T

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Brookhaven Science Associates U.S. Department of Energy

Field in Iron Field in Iron

40 45 50 55 X

  • 100
  • 50

50 100 Y 50 100 150 200 Z

  • 100
  • 50

50 100 Y 50 100 150 200 Z 40 45 50 55 X

  • 100
  • 50

50 100 Y 50 100 150 200 Z

  • 100
  • 50

50 100 Y 50 100 150 200 Z

2.1 T

Without Permanent Magnet With Permanent Magnet

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Brookhaven Science Associates U.S. Department of Energy

Field in Midplane Field in Midplane

Midplane Field in NSLS Sextupole

  • 1.5
  • 1
  • 0.5

0.5 1 1.5 20 4 0 60 80 100 120 140 160 180 200 X (mm) Bz (Tesla) B (no PM) B (with PM)

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Inserting Block Inserting Block

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Field vs. Current Field vs. Current

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Superconducting Wiggler Superconducting Wiggler

Replace existing 5 pole, 4.7 T wiggler Three operating modes

  • 11 Poles, 3.0 T (+2 half-strength poles at ends)
  • 5 Poles, 4.7 T
  • 1 Pole , 5.5 T

Extremely low heat leakage

  • 0.35 l/hr liquid helium use
  • No refrigerators, filled from dewar
  • High TC leads in neck

BAD MISTAKE

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Brookhaven Science Associates U.S. Department of Energy

Wiggler Characteristics Wiggler Characteristics

Period

17.16 cm

Number of Poles

13

Maximum Field

5.5 T

Horizontal Beam Aperture

5.95 cm

Vertical Beam Aperture

1.95 cm

Good Field Region

±5 mm

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Brookhaven Science Associates U.S. Department of Energy

Allowed Field Errors Allowed Field Errors

OPERATION RAMPING

Dipole (?

Bydz) 1.00 G-m 5.00 G-m

Skew Dipole (?Bxdz)

1.00 G-m 1.00 G-m

Quadrupole

110.00 G 110.00 G

Skew Quadrupole

150.00 G 150.00 G

Sextupole

29.00 KG/m 29.00 KG/m

Skew Sextupole

10.00 KG/m 10.00 KG/m

?

? Byd2z 2.00 G-m2 5.00 G-m2

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Wiggler Operating Modes Wiggler Operating Modes

Full Wiggler Partial Wiggler Wavelength Shifter

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Synchrotron Radiation Spectrum Synchrotron Radiation Spectrum

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Why 33 KeV? Why 33 KeV?

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Digital Subtraction Angiography Digital Subtraction Angiography

Excised pig heart with iodine contrast agent injected into coronary arteries

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Imaging Imaging

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Clinical Program Clinical Program

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Wiggler Construction Wiggler Construction

Extremely low carbon Remko B iron

  • Minimizes residual magnetization

NbTi Wire

  • 1:1 Nb:Ti ratio

Coils divided radially into two sections:

  • Minimizes current in high field region near pole
  • Inner coil wire: 1 mm dia., 285 A/mm
  • Outer coil wire: 0.7 mm dia., 485 A/mm
  • Maximum current 295 A

Stored Energy 170 KJ

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Cryostat Cryostat

Warm bore-cold iron 4.5 K He bath Insulated bore tube Heaters to keep beam pipe above freezing 20K shield cooled by He boil-off 80K liquid nitrogen cooled shield High TC leads in LN2 pot

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Electrical Characteristics Electrical Characteristics

Ramping rate (1.1 T to max)

1.14 T/min

Voltage during ramp

16.5 V

Passive quench protection

  • Diode-resistor networks across coils in cryostat
  • Power can safely stay on during quench
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Wiggler Picture Wiggler Picture

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Status Status

Wiggler constructed by Oxford Instruments, field mapped Delivered to BNL, Spring 1998 Vacuum leak discovered, returned to Oxford Repaired at Oxford Delivered to BNL, Fall 1999 High TC lead exploded when powered Returned to Oxford

  • They believe lead may have been damaged in transit
  • Bad mechanical design, high stress on brittle lead

Delivery expected Spring 2002

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Small Gap Undulators Small Gap Undulators

Radiation wavelength λo = (λu/2γ2)(1+K2/2) K = 0.934 Bu[T] λu[cm] peak field Bu ∝ exp[-πG / λu] High photon energy ⇒ Short radiation wavelength ⇒ Short undulator period ⇒ Small gap

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Brookhaven Science Associates U.S. Department of Energy

Hybrid Undulator Hybrid Undulator

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Pure Permanent Magnet Undulator Pure Permanent Magnet Undulator

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Prototype Small Gap Undulator Prototype Small Gap Undulator

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In-Vacuum Undulator In-Vacuum Undulator

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Mini-Gap Undulator Mini-Gap Undulator

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Undulator Location Undulator Location

97 cm Quadrupoles Reduces βv, min from 32 to 16 cm Reduces minimum gap from 3.3 to 2 mm

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Mini-Quadrupole Mini-Quadrupole

13 Amps 172 Turns

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Undulator + Quadrupoles Undulator + Quadrupoles

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Small Gap Undulator Parameters Small Gap Undulator Parameters

PSGU IVUN MGU (mini-β) Period λu 16 mm 11 mm 12.5 mm Magnet Gap 6 mm 3.3 mm 3.3 mm (2.0 mm) Peak Field Bu 0.62 T 0.68 T 1.0 T (1.66 T) Kmax 0.93 0.70 1.17 (1.94)

  • Fund. Energy 3.2 Kev

5.4 KeV 3.5 KeV (1.76 KeV) Beam Energy 2.8 GeV 2.8 GeV 2.8 GeV

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MGU Spectrum MGU Spectrum

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MGU Measurement MGU Measurement

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MGU Field Measurement MGU Field Measurement

MGU-13 Mapping

  • 10
  • 8
  • 6
  • 4
  • 2

2 4 6 8 10 50 100 150 200 250 300 350 400 450 500 550

Z (mm)

Byavg

After Adjusting Taper by 0.14 mm. Gap - 3.3 mm

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MGU First Integral MGU First Integral

MGU-13: 1st Integral of By

  • 2.5
  • 2
  • 1.5
  • 1
  • 0.5

0.5 1 1.5 2 2.5 50 100 150 200 250 300 350 400 450 500 550

Z (mm)

1st Int.By

After adjusting taper by 0.14 mm; Gap = 3.3 mm

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Brookhaven Science Associates U.S. Department of Energy

MGU Second Integral MGU Second Integral

MGU-13: 2nd Integral of By

  • 0.6
  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.1 0.2 0.3 0.4 0.5

50 100 150 200 250 300 350 400 450 500 550

Z (mm)

2nd Int. By

After adjusting taper by 0.14 mm; Gap = 3.3 mm

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Summary Summary

Permanent magnet assisted sextupole

  • Adding permanent magnet material can increase pole tip

field by reducing saturation in iron

  • Simple method of upgrading existing magnets

Superconducting Wiggler

  • Potentially versatile design
  • Problem with HTC leads

Mini-gap Undulator

  • Latest NSLS short period, in-vacuum undulator
  • Highly tunable source of hard x-rays from relatively low

energy storage ring