Control Dewar

Beam Injection

DC current

Rf power

Rf power

Liq. HeSRCCryogenic activities in RIKEN RI beam factory

Table of Contents

1: Overview of RIBF and SRC

2: Operation of SRC cryogenic cooling system

3: Current issues in the cryogenic system for SRC

4: A new He refrigerator for SRF linac

H. OKUNO

RIKEN, Nishina Center for Accelerator-based Science

RIKEN RI Beam Factory (RIBF) (2006-)The world’s most intense RI Beams over the whole range of atomic masses to

open and develop new fields of nuclear science

Powerful Heavy Ion Accelerator (Projectile Fragmentation or in-flight fission)

18GHz ECRIS

RILAC

RRC

fRC

IRC

SRC

400MeV/u (Light Ion)

345MeV/u (Very Heavy Ion, Uranium)

I = 1pmA (6 x 1012 #/s)

New Cyclotron System

18GHzECR+RILAC+RRC+ｆRC+IRC+SRC

Ion beam Target

RI beam

Target

SC magnets with cryogenic system for RIBF

28GHz SC ECR ion source

GM/JT-cooler (2.5W@4.3K)

SRC with TCF200s

(1000W@4K)

5 STQs for BigRIPS

with TCF50 (320 W@4K)

21 STQs for BigRIPS

with 21 GM/JT-coolers

(2.5 W@4K)

1 SDQ for SHARQ

with (2.5 W@4 K)

SAMURAI magnet

with 2 GM/JT-coolers (2.5 w@4.5K)

RIBF needs SC magnets

High magnetic rigidity (large M/Q)

Energy Saving

Large aperture for secondary beams

25 GM/JT-coolers

2.5 x 25 = 63 W@4K

Superconducting

Bending Magnet

Control DewarSide Shield

(Open for maintenance)

SC Main Coil

SC Trim CoilLower Shield

RF-Cavity

Upper Shield

Upper Yoke

Side Yoke

Lower Yoke

The World’s First Superconducting Ring Cyclotron (SRC) H. Okuno et al., IEEE Trans. Applied Superconductivity, 17 (2007) 1063

Self Magnetic ShieldSelf Radiation Shield

Sector Magnets :6RF Resonator :4Injection elements.Extraction elements.

Main Spec. of SRCK = 2,600 MeVMax. Field: 3.8 T (235 MJ)RF frequency: 18-38 MHzTotal Acc. Volt.: 640 MVWeight: 8,300 tonsDiameter: 19 m Height: 8 m

Superconducting Sector Magnet

Unfolded diagram

SC Conductor

Small amount of mineral impurity:

Yield Strength > 56.2 MPa

(cf. 40 MPa for pure Al)

RRR of Al > 803

Two types of the S.C. coils

Main coil: bath cooling (stabilized)

Trim coil: indirect cooling by force two

phase helium

Assembling of SRC in the vault

Reservoir Tanks

Compressor

Refrigerator

Turbine JT-valveHeat exchanger

Control dewar

SRC

R.T. 4.5 K100 m3 (2 MPa) x 4

74 g/s of 1.65 MPa GHe

He cooling system for the SRC

Cooling Capacity Heat Load

@4.5 K 620 W (1.3 x H.L.) 470 W

@ 70 K 4000 W 2800 W

For cooling of P. L. 4 g/s 3 g/s

Initial cooling 21 days (142 ton)

0

50

100

150

200

250

300

350

H17.9.15 H17.9.20 H17.9.25 H17.9.30 H17.10.5 H17.10.10 H17.10.15

Day

Tem

p (K

)

TI_A1P01

TI_A1P02

TI_A1P03

TI_A1P04

TI_A1P05A

TI_A1P05B

TI_A2P01

TI_A2P02

Calc.

T(Sup.)

T (Cold Mass, Ret.)

Calculation

23 Days

DT< 50K

Cool-down curve in the first trial

Control Dewar

Beam Injection

DC current

Rf power

Rf power

Liq. HeSRC

Beam profile at the exit of SRC

The First Beam 2006/12/28!

Intensity upgrade at RIBF

RILAC2RRC

SCECR

fRC IRC

SRCHe gas Rotating Be diskAccelerators

He gas stripperRotating Be diskfRC upgrade(K570=>K700)

RIBF starts!

The new injector(RILAC2) starts!

Transmission of the beam: improvedStability of the devices: improved

Germany/GSI

28-GHz SC-ECR

73 pnA U (~4x1011#/s 2017)

supported by the continuous efforts for stable operation of cryogenic system.

Summary of 10 year operation Season Operation (h) Steady operation

(h)No. of

failure Repair (h) Availability

05/'06 4293.5 1858.6 2 188.3 0.958

2005/11/8 - 2006/3/10: broken ceramics of a feedthrough in the liquid He vessel

06/'07 7804.8 6452.6 5 1089.9 0.877

07/'08 1274.0 405.3 0 0.0 1.000

2008/2/11 - 2008/8/20: Oil contamination in the He refrigerator and making additional oil separator

08/'09 6785.1 5180.3 0 0.0 1.000

09/'10 5515.1 3659.9 1 20.2 0.996

10/'11 6505.3 4537.5 1 2.6 1.000

11/'12 7463.7 5154.1 1 144.2 0.981

12/'13 6240.8 3315.5 1 169.0 0.974

13/'14 3672.6 2475.9 5 99.9 0.974

14/'15 6553.3 4031.2 5 11.9 0.998

Total 56108.4 37071.1 21.0 1725.9 0.970

What happened on 8th November , 2005(7th Nov, 2005: The 1st excitation to the maximum current)

All turbines tripped, liquid He level quickly fell to zero, and thermal insulation vacuum worsened.

The emergency valve opened.

A feed through attached the Liq. He vessel

Wall of the liq. He vessel (2000 L)

The feed through for the indirectly cooled S.C. trim coils

CeramicsCupper Crack

Don’t repair it, replace it.

Smaller ceramics => small risk

Flow rate through the first turbine

(Manually adjusted)

Oil contamination in the He refrigerator

The He refrigerator was contaminated with oil from the He compressor. (Feb. 2008)

2005-2007

2008

Heat exchangers : washCharcoal in the 80K adsober : replaceOil separator of the He comp. : 4step→6 step

HX1-3

HX4-5

Heat exchanger in the He refrigerator

Cut the heat exchanger unit from the refrigerator

Battle against the oil in the He refrigerator

Cleaning process in a factoryAccess to the lower temperature region

Oil in the refrigerator: 2000 cc => 4 cc

5th

Sep

erat

or

4th

Sep

erat

or

3rd

Sepe

rato

r

1st

Sep

erat

or

2nd

Sepe

rato

r

1.5

th S

epe

rato

r

Compressor

Unit A

Uni

t B

Uni

t C

High Pressure Line

Low Pressure Line

Additional oil separator in He compressor unit

Demister

Coalescer

Charcoal+

Mole. Sheave

Charc

oal

Ne

w

New

Oil contamination: 100 ppb -> 20ppb

Current issues in the operation

• Radiation damage of epoxy bonding in the superconducting trim coils

• Malfunction of the cryogenic control system

• Shortage of He gas

Neutron damage to SC trim coil

Support plate (Al-alloy)

Cooling tubeInsulator

Screw

The epoxy bonding is important to coolthe coil. Its radiation hardness should be Studied.

Cross section of SC trim coil

Lifetime of epoxy glue = lifetime of SRC

Electrostatic deflection channel and SC trim coil

EDC for Beam extraction

Beam loss point

SC trim coil

Be

am

Al sample to monitor neutron flux

g Emitted in the b decay of 22Na made in the reaction of 27Al (n, 4n2p)22Na

Dose to Sc Trim coil < 0.1 MGy/10 yearWe can use it for more than 100 years.

Valley of SRC

Sector magnet of SRC

He refrigerator

Cryogenic Control system for SRC

LAN for cryogenic control

VME1

I/O panel

VME2

I/O panel

Reflective memory

Cont. Panel for P.S.s

SRC

Valve controlTemp. monitoretc.

Valve controlTemp. monitoretc.

DC Power SuppliesQuench Detectors

PC

PC

We are suffering from coil shut down due to fake events

Action ConditionFast shut down and isolation ofthe He refrigerator

Quench.Bad thermal insulating vacuum.

Slow shut down Compressor or turbine trip.High or low liquid He level.High temp. of the S.C. coils.Low flow of gas He to P.L.High temp. of P.L.Low flow of liquid He to the S.C. trimand SBM.

Example of the troubles due to fake events.1: Slow shutdown due to high temperature of one of the main coil (no sign in the trend graph)2:Turbine trip due to high speed of the turbine ( no sign in the trendegraph)…….. It’s a time to replace it!

Shortage of helium gasThe cooling system is closed cycle but tiny leak is inevitable.

Trend of price and import of Helium gas.

We were operating with a He leak from 2012 to 2013. We need supply 1000 m3/year in operation.

Now we can not operate the system with such leak.

He gas volume in the buffer tank

Helium refrigerator Joint box

Valve boxes

Transfer tube

Coaxial line

New He refrigerator for Superconducting LINAC

First He refrigerator from Air liquide

By courtesy of Yonekura (AirLiquide Japan)

RILAC upgrade

Requirement from the Cryo modules for the Superconducting RILAC

Outline value unit commentsNo. of SRF 2, 4/CM

No. of Cryomodule 3Temperature 4.5K

liquid N2 yes thermal shieldCold mass

Nb 120, 240kg/CM 2, 4 cavitiesTi 60,120kg/CM 4 He jackets

SUS 80kg/CM 4 tunersSUS 100kg/CM He tankSUS 50kg/CM He pipingTotal 590kg/CM

4 Cryomodule 1475kgHeat load

Dynamic 48W/CMstatic 12W/CM

4.5K Total 150WTemperature of thermal Shield 80K

Heat load to thermal shield 120W80 K total 300W

Inventory 300LAllowable pressure fluctuation 4.00E-04Mpa 4 hPa

The cooling power 600 W! (4 times)

Cooling diagram

He

bu

ffer

tan

k

Load valve

Unload valve

He comp. Oil sep.

Co

ld b

ox

LN2 CE tankLN2 Vent. tank

4 cavities 4 cavities 2 cavities

4.5 K gas He returnLiq. He supply

Pre

coo

ling

80K shield cooling

80K shield cooling

Liq

. He

sup

ply

4.5

K g

as H

e re

turn

Commissioning test of Cold BoxThe refrigeration system is consisted by screw compressor and cold box.

main feature is in below

Compressor : 1.75MPa (18.5BarA)

74.2g/s

Cold box 600W@4.5K

This cold box is consisted by the 2 turbines in series with JT valve.

During the commissioning process, we had achieved to

- 700W @ 4.5K by the heater in Phase separator.

This is only operation of cold box for checking the performance, but system operation condition is shown in left graph and it is demonstrated of stable operation

By courtesy of Yonekura (AirLiquide Japan)

Commissioning test of whole systemTotal cooling test was organized at the same time to cooling down with CB.

After starting the turbine, system was reached to 4.5K in cold part and filled by the LHe on CMs.

With achieving following criteria, we had measured of performance.

CB operates maximum power.

to keep the LT 88% at CM.

pressure in CM 24.6kPa (1.26barA)

phase separator keeps 50% of LHe.

then, we measured the performance with keeping the criterion and we could record that CB seemed to be still kept of 400W@4.5K as average in its cold power

By courtesy of Yonekura (AirLiquide Japan)

Summary•The SRC was successfully operated for 12 years as the final booster of RIKEN RIBF accelerator complex after the first beam at the end of 2006. •The operation of the cryogenic cooling system was also stable despite the two big troubles.

•The He leak to the thermal insulation vacuum of the magnet through a tiny crack in the feed through attached to the liquid He vessel. •The oil contamination in the He refrigerator.

•The current issues for superconducting magnets •Radiation hardness of the superconducting trim coils •Trouble in the cryogenic control system•Shortage of helium gas

•The He refrigerator for the SRF in RILAC were successfully installed and commissioned. The new RILAC will have the first beam around the end of this year.