Vladimir Kashikhin

Technical Division R&D Retreat

January 26, 2016

Compact Cryogen Free HTS Magnets for

Linear Accelerators

• Introduction

• Linear Accelerator NbTi Magnets R&D

• NbTi magnets for SCRF Cryomodules

• Novel Configuration of SC Magnets with Circular Coils

• Novel Approach to Linear Accelerator Magnets String

• HTS Magnets for Linear Accelerators

• Proposed HTS Magnets R&D

• Summary

Outline

1/26/20162 Vladimir Kashikhin | TD R&D Retreat

• Several years ago was initiated R&D by M. Ross, J. Kerby, A.

Yamamoto to design and build NbTi superconducting magnet for

SCRF Cryomodule of Linear Accelerator.

• It was investigated a novel approach: a splittable magnet

configuration (proposed by Akira Yamamoto) combined with a

conduction cooling.

• R. Kephart and R. Stanek supported this R&D and allocated

funds from US-Japan collaboration.

• Two model magnets were built at FNAL and successfully tested

at KEK and FNAL. KEK magnet was installed in the KEK

Cryomodule.

• On the base of this R&D were built and tested two magnet

prototypes for LCLS-II Linear Accelerator.

• Successful tests of both prototypes open the way to manufacture

33 LCLS-II production magnets.

1/26/2016 Vladimir Kashikhin | TD R&D Retreat3

Introduction

1/26/2016 Vladimir Kashikhin | TD R&D Retreat4

Magnet Package Inside SCRF Cryomodule

1/26/2016 Vladimir Kashikhin | TD R&D Retreat5

Magnet Package Configuration

• The magnet has 4 superconducting racetrack type coils, iron yoke with field clamps.

• At the magnet pole tip distance of 90 mm, and 120 mm pole length the magnetic field has large amount of end fields.

• First level bullet [24pt Reg]

1/26/2016 Vladimir Kashikhin | TD R&D Retreat6

Magnet Package fabrication

1/26/2016 Vladimir Kashikhin | TD R&D Retreat7

Conduction Cooling Test at STC

The pre-prototype magnet was mounted inside STC cryostat and tested in close to the cryomoduleconditions.There were verified the magnet and conduction cooled leads performance.

The main idea of the proposed magnet is to use

circular coils to generate a quadrupole field. The

magnetic flux in this case should be directed around

this coil to magnet poles constituting a quadrupole

configuration. This geometry was proposed by

I.F. Malyshev for room temperature magnets. But

now is most suitable for superconducting coils having

a much smaller cross-section than room temperature

coils.

1/26/2016 Vladimir Kashikhin | TD R&D Retreat8

Novel Design of SC Magnets with Circular Coils (MT21)Parameter Units Aperture

80 mmAperture 45 mm

Quadrupole pole tip diameter mm 90 45

Peak field gradient T/m 5.54 10.2

Quadrupole length mm 50 50

Coil ampere-turns kA 8 4

Peak field in the coil T 0.4 0.3

Iron yoke peak field T 2.2 2.12

Integrated gradient T 0.43 0.71

Effective length at max gradient mm 78 70

Outer yoke diameter mm 300 150

Single coil quadrupole has

the solenoidal field

component Bz=0.045 T. Two

coils design configuration

eliminate the integrated

solenoidal field.

Circular coils are suitable for

using HTS superconductor.

1/26/2016 Vladimir Kashikhin | TD R&D Retreat9

Multi Coils SC Quadrupole (MT21)

0

1

2

3

4

5

6

7

8

-0.6 -0.4 -0.2 0 0.2 0.4 0.6Z, m

Gra

die

nt,

T/m

One Coil

Two Coils

Four Coils

-0.04

-0.03

-0.02

-0.01

0.00

0.01

0.02

0.03

0.04

0.05

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

Z, m

Bz, T

One Coil

Two Coils

Four Coils

This SC magnet configurations were presented and published at MT21, 2009

It is possible to use circular coils also for multipole magnets.

Recently INFN started R&D of such sextupole magnet configuration

based on MgB2 superconductor. The presentation by G. Volpini

attracted the great interest at MT24, S. Korea, 2015.

1/26/2016 Vladimir Kashikhin | TD R&D Retreat10

SC Sextupole with Circular Coils (MT21)

Parameter Units Aperture 80 mm

Aperture 45 mm

Sextupole pole tip diameter mm 90 45

Peak field gradient T/m2 102.8 388.5

Sextupole length mm 100 100

Coil ampere-turns kA 5 2.5

Peak field in the coil T 0.4 0.24

Iron yoke peak field T 2.71 2.54

Integrated gradient T/m 11.7 44.1

Effective length at max gradient

mm 114113

Outer yoke diameter mm 270 135

The novel approach is to use the possibility of

superconducting magnets to work in the

persistent current mode. MRI solenoids routinely

use this technique. The main magnet system’s

parameters should be in an agreement with the

following: large magnet inductances; very low

splice resistances; high performance persistent

current switches; long low inductance

superconducting busses; efficient control

system.

1/26/2016 Vladimir Kashikhin | TD R&D Retreat11

Novel Approach to LC SC Magnet System (MT22)

Single cell schematic

1/26/2016 Vladimir Kashikhin | TD R&D Retreat12

Superconducting Switch (MT22)

Two superconducting switches were built and tested.

Need R&D funds to test them initially with NbTi superconducting

quadrupole to verify the system performance in the persistent

current mode. Later HTS switches should be designed and build.

1/26/2016 Vladimir Kashikhin | TD R&D Retreat13

R&D Schedule

Design and build superconducting quadrupole with circular

coils based on HTS superconductor (2016).

Update the MTF Stand 7 to test magnets in the conduction

cooling mode at different temperatures provided by the

cryocooler (2016).

Investigate the HTS magnet performance at Stand 7 (2017).

Test at Stand 3 the NbTi quadrupole with the existing two

superconducting switches (2016).

Investigate the quadrupole magnetic center stabilization in the

persistent current mode of operation (2017).

Design and build HTS superconducting switches (2017).

Investigate the HTS magnet and switches performance (2017).

Build and test the stand alone HTS magnet unit (2018).

1/26/2016 Vladimir Kashikhin | TD R&D Retreat14

Summary

The proposed R&D plan will provide further progress in the

accelerator magnets technology.

The novelty is based on the integration of: new magnet

configurations, advanced HTS superconductors,

superconducting switches, persistent current mode of

operation, cryocooler.

Positive effects: magnet with higher operation temperature,

more efficient and less costly cooling, elimination of long

magnet power cables, high magnetic field stability, high

magnetic center stability, low energy consumption.

The program is scheduled for three years.

There will be used to some extent existing magnets, parts,

equipment, test Stands, and unique FNAL experience.

For the phase one in 2016 is needed 100 k$ M&S, and 1 FTE

Labor.