Some considerations on Cryogenic system for 9-cell SC

cavities test at IHEP

Accelerator research centerShaopeng Li

The Third IHEP-KEK 1.3GHz SC Technology Collaboration Meeting

Dec. 7-8, 2010, IHEP, Beijing

contents ： Horizontal test stand of BEPCII 500MHz

SC cavities Some considerations on cryogenic

system for 2K 9-cell cavities test at IHEP

Layout of BEPCII cryogenic system

Cryogenic hall and tank farm

Facilities

He compressor systems, VFDs, air compressor, air drier, ORS, cooling-water system, spare power engine, gas tank farm, control system

Tank farm Tank farm

Two 130m3 ,1.45Mpa Two 130m3 ,0.73Mpa One 30m3 ,0.08Mpa One 5m3 ,6Mpa One 10m3 ,0.73Mpa

SRF Cavity(On line)

SRF Cavity test stand

Multi-channel transfer line

SRF quench line

Waveguide

LHe dewar SRF valve box

500W refrigerator

LN2 transfer line

BEPCII second colliding hall

heater

UPS

PLC rack

Horizontal test stand for BEPCII 500MHz SC cavities

Horizontal

test stand

500MHz

SC cavityOperation position

Some considerations on 9-cell SC cavities test

The feature of vertical test of 9-cell SC cavity• Short term test, low power test

• Open cycle and Close cycle system• Open cycle :normal test cryostat, but recovery and purify system ；• Close cycle: special test cryostat with tight leakage

• Depressurized pumping system ；• Off-line or on-line liquifier/refrigerator

The feature of horizontal test of 9-cell SC cavity• Continuous and long term running

• Close cycle system, high power test

• Depressurized pumping system ；• On-line liquifier/refrigerator

Flow diagram of Vertical test

Pure storage tank

Pure storage tank

80K purifier

LHe mobile D

ewar Vertical test stand

pump Gas bag Recovery compressor

Impure storage tank

Pure storage tank

Liquifier/refrigerator Vertical test stand

pump

Open cycle

Close cycle

Liquifier Storage dewar

Helium liquified plant

Flow diagram of vertical/horizontal test

Recovery&purity system

Pumping unit Heat exchangeHeater

2K ValveBox

4K Valve Box

2000LDewar

500W4.5K

refrigeratorMain Comp.

Horizontal test stand

Vertical teststand

Normal methods to 2K

Case 1 ： Directly to depressurize saturated vapor pressure of helium

Case 2 ： Depressurization + JT ； Case 3 ： Depressurization +JT + Hex ；

Case 1 ： Directly to depressurize Directly to depressurize the saturated va

por pressure of LHe in test cryostat by pumping system and then the low temperature can be produced

Vertical testcryostat

Pressure （ KPa ） 24.04 5.33 3.13 1.64

Temperatuer（ K ）

3 2.2 2 1.8

Pumping system

Total heat loss Q=100W

1.8K ，16mbar

During the SC cavities test, the LHe of test cryostat will be consumed and LHe level will be lowered ；

The heat loss of 1W@1.8K will consume 1.08L/h

To assume total heat load 100W ， the mass flow rate will be LHe 4.37g/s and LHe consumption is 108L/h

Case 2 ： Depressurization + JT The LHe throttled directly to test dewar from storage dewar ； Isoenthalpy thrrotle h1=h2 =h2Gx+h2L(1-x) ， h1 is enthalpy

value at 4.2K ； h2G and h2L are enthalpy at 1.8K LHe and GHe ； x is helium fluid quality ；

Energy equation ： mh2+Q=mh4 ， h4 is enthalpy at 1.8K GHe ， m is mass flow rate

The produce of liquid helium is about 61% from 4.2K to 1.8K

If total heat loss is 100W ， the total mass flow rate of helium is around 7g/s

3

Verticaltest dewar

Toatl heat loss Q=100W

pump 2000L Dewar

Saturated LHe4.2K ， 1.0bar

1.8K ，16mbar

1

24

JT

T-S diagram

Case 3 ：Depressurization +JT+ heatexchange

The flow pass through the heatexchange to be cooled by return cold GHe and then it will be throttled to more low temperature by JT ；

3

Vertical Test de

warTotal heat loss

Q=100W

Pump 2000L dewar

Saturated LHe4.2K ， 1.0bar

1.8K ，16mbar

1

5

4JT

6

T 5

（ K ）4.2 3 2.2

1-x 61% 80% 87.7%

m(g/s) 7.01 5.38 4.88

2

Comparison of three methods

Case 1 ： No JT and HEX, Ease operation and simple. But it has to be interrupted when

the LHe level lower to the value of limitation and then refilling LHe again.

Case 2 ： No heatexchange ， lower efficiency. But it can maintain and extend the test time

Case 3 ： Complex ， higher efficiency. It’s normal to be used in cryogenic system of accelerator.

Calculation of pump speed

Temperature K

Density of saturated liquid

g/l

Latent heat J/g

Density of saturated vapor

g/l

Pressure of saturated vapor Pa

Density at pump inlet at 300K

g/l

1.8 145.42 22.977 0.45469 1638.4 2.6291E-03

2.0 145.65 23.046 0.7936 3129.3 5.0215E-03

300K/1bara / / 0.1604 / /

Temperature K

Heat load W

Mass flow g/s

Volume flow m3/h

Volume flow at outlet

at 300K@1bara m3/h

Volume flow at pump inlet

at 300K m3/h

1.8 20 0.870 6.892 19.536 1191.879

2.0 20 0.868 3.937 19.477 622.162

1.8 50 2.176 17.229 48.840 2979.697

2.0 50 2.170 9.842 48.694 1555.405

1.8 80 3.482 27.567 78.144 4767.515

2.0 80 3.471 15.747 77.910 2488.648

1.8 100 4.352 34.458 97.680 5959.394

2.0 100 4.339 19.684 97.387 3110.810

Performance curve of Edwards EH1200 Roots pump

1mbar is the limitation of vacuum of

Mechanical pump

1000m3/h

Equivalent heat load at 1.5K for 1.8K design

Temperature K

Heat load WMass flow g

/s

Volume flow at 300K/1638.4Pa

m3/h

Equvalent mass flow at 300K/47

1.54Pa g/s

Equvalent heat load at 1.5K W

1.8

10 0.435 595.939 0.125 2.783 3.6 times

20 0.870 1191.878 0.250 5.566

50 2.176 2979.697 0.626 13.917

100 4.352 5959.394 1.253 27.834

Heat power to room temperature for return pipe

Temperature KEnthalpy of cold GH

e J/gPressure of saturated

vapor Pa

Enthalpy of 300K at saturated vapor

pressure J/g

Difference value of Enthalpy J/g

1.8 24.201 1638.4 1573.2 1548.999

2.0 25.041 3129.3 1573.2 1548.159

Temperature K Heat load W Mass flow g/s Heat power W

1.8 20 0.870 1348.30

2.0 20 0.868 1343.54

1.8 50 2.176 3370.76

2.0 50 2.170 3358.85

1.8 80 3.482 5393.22

2.0 80 3.471 5374.15

1.8 100 4.352 6741.52

2.0 100 4.339 6717.69

Recovery and purify system

VACUUM

COMPRESSOR 4.5g/s

INTEGRATED TUBE PURE HELIUM 4000Nm3

INTEGRATED TUBE IMPURE HELIUM 4000Nm3

GHe BAG 50-100m3

10-20 m3

LN2 TOWERPURIFIER

4.5g/s

AMBIENT HEATER 300m3/h

ROOTS PUMPS STATION

LHe OUTLET TO REFRIGERATOR

LHe INLET FROM REFRIGERATOR

EACH ROOTS PUMP PUMPING SPEED 500-1000m3/h TO HELIUM

TEST STATION

1.8K SYSTEM

Recovery & purify systen

LN2 INLET

GN2 OUTLET

Summary

The pump speed will be choosed according to the heat loss of 20W at 1.8K, that is around the capacity of 1000m3/h

The capacity of recovery and purify system are to be thought with the heat loss of 100W at 1.8K and the capacity will be 100m3/h or 4.5g/s

The design and calculation in detail for 2K test system are still underway

Tanks for your attention ！