Cryogenics for particle Accelerators · magnetic field - B < 2 Tesla –Iron Yoke and normal magnet B < 5.5 Tesla –Superconducting magnet of Nb-Ti wire at 4.2 K B ~ 8-10 Tesla -

Cryogenics for particle Accelerators

Sandip Pal

VECC, Kolkata

What is Cryogenics ?• Kryo – Very cold (frost)

• Genics – to produce

• Cryogenics is a branch of physics which studies the methods to obtain temperatures below 123 K or -150°C.

• Main broad applications of cryogenics are

i) Liquefaction and separation of gases

ii) Storage and transport of gases

iii) Alternate material and fluid properties at low Temp

iv) Biological and medical applications

v) Superconductivity: Zero Ω and Magnetic flux expulsion

vi) Vacuum

vii) Cryogenic Engine

Superconducting Devices

31/01/2020 IJAS-2020 VECC Kolkata 3

Applications : Gas Industry

• Liquefaction

• Separation

• Storage

• Purification


Applications : Superconductivity

• Large scale superconducting magnet

• Superconducting RF Cavity

• MRI

• Squids

• Maglev Locomotion

• Transformers and Generators

Superconducting Cyclotron31/01/2020 IJAS-2020 VECC Kolkata 5

Outline of the talk

• Criticalities in Cryogenic Technology

• Cryogenic Fluids

• Thermodynamics

• Material properties used for cryogenics

• Generation of cryogenics

• Cryogenics for SCC at VECC

• Cryogenics for RIB e-Linac at VECC


Design & operation criticalities

Heat budget & load type selection

Selection of liquefier and subsytems

Arrangement and Placement of systemPipelines ΔP & cryolines

High pressure gas storage & pipelines

Selection of materials in terms of strength, expansion, Heat transfer properties

Cryogenic storage, cryostat and distribution

Leak and impurity ingress especially moisture

Pressure safety system

Cryogenic instrumentation magnetic effect & thermal stress – temperature, pressure, level, flow, heater, cabling, and calibration

Thermal cycling

Asphyxiation & safety PPE

Cleaning, evacuation and purging

Water Cooling system


Gas Management System & Purification

Useful range of cryogens


Properties of Cryogens

Property He H2 N2 O2 Ne

Normal boiling point [K] 4.22 20.4 77.4 90.2 27.2

Critical temperature [K] 5.20 33.2 126 155 44.4

Critical pressure [bar] 2.3 13.2 34 50.8 27.2

Triple Point Temp. [K] 2.17* 14.0 63.1 54.4 24.6

Triple Point Pr. [mbar] 50.4* 72 128 1.5 432

Liq./Vap. density 7.4 53.2 176 240 127

Heat of vaporization [J.g-1] 20.4 446 199 213 86.6

Liquid viscosity [mPl] 3.3 13 152 188 124

(*) Lambda Point31/01/2020 IJAS-2020 VECC Kolkata 9

Vaporization of normal boiling cryogens under 1 W applied heat load

Cryogen [mg.s-1][l.h-1]

(liquid)[l.min-1]

(gas NTP)

Helium 48 1.38 16.4

Nitrogen 5 0.02 0.24

Using Latent Heat onlyLatent heat and enthalpy of gas

LHe from 290 to 4.2 K 29.5 lit 0.75 lit

LHe from 77 to 4.2 K 1.46 lit 0.12 lit

LN2 from 290 to 77 K 0.45 lit 0.29 lit

Amount of Cryogens Required to cool down 1kg Iron


Cryogenics in particle accelerators

• Accelerators are electromagnetic machines, which exert forces on beams of charged particles via electric & magnetic fields for accelerating, guiding and focusing them.

• Absence of electrical d.c. resistance, or limited a.c. dissipation in superconductors opens the way to produce higher fieldsand thus higher beam energy, while containing dimensions of particle accelerators.

• Circular accelerators to handle stiffer high energy beams require increase in radius of circular path, bending radius and magnetic field - B < 2 Tesla – Iron Yoke and normal magnet B < 5.5 Tesla – Superconducting magnet of Nb-Ti wire at 4.2 K B ~ 8-10 Tesla - Superconducting magnet of Nb-Ti wire at 2 K


Phase diagram of helium


Helium as a cooling fluid

Phase Domain Advantages Drawbacks

Saturated He IFixed temperatureHigh heat transfer

Two-phase flowBoiling crisis

SupercriticalMonophaseNegative J-T effect

Non-isothermalDensity wave instability

Saturated Helium IILow temperatureHigh conductivityLow viscosity

Poor Dielectric StrengthCostSub-atmospheric

Pressurized Helium II

AdditionallyPrevented from air inleaksIsolation voltage ~ kV range

CostLiquid to Liquid HX


Basic Engineering Thermodynamics

0H C

Q Q W

0CH

H C

QQ

T T

1st Law of Thermodynamics: conservation of energy

2nd Law of Thermodynamics - Clausius Law of (In)equality

Entropy is either constant or increased but never decreased

_ 1H

C

TCarnot Factor

T

Carnot factor defines the minimum amount of work necessary to extract heat at a low temperature and reject it at a higher one.

• The Carnot factor clearly demonstrates why in cryogenic system heat entering the low temperature level should be limited to the necessary minimum.

• The refrigeration work in real systems is always above the limit given by the Carnot factor due to inevitable entropy losses.

1 W at 4.2 K is equivalent to 70 W at 300 KC H

C H

Q Q

T T

ΔQH TH

ΔQC TC

ΔW∆𝑊 ≥ ∆ ሶ𝑄𝐶

𝑇𝐻𝑇𝐶− 1


Carnot, Stirling and Eriction Cycle


Joule-Thompson ProcessWinComp.

12

Load

HX

JT

S

TmL

mL

12

34

Q

Claude Process: combination of Brayton & JT processes

mL Q

WinComp.

12

LoadJT

S

TmL12

3

6

HX

HX

HX

Wout

Expander

4

5 7

8

3

4

5 6

7

8

For helium, inversion temperature < ambient – not possible to liquefy only by JT process31/01/2020 IJAS-2020 VECC Kolkata 16

Claude Refrigeration Cycle


Basic Engineering Thermodynamics

Exergy analysis provides the greater insight into the influence of irreversible losses on the cycle performance.

Exergy balance equation of a thermodynamic cycle is

𝑗

ሶ𝑄𝑗 1 −𝑇0𝑇𝑗

− ሶ𝑊 + ሶ𝑚𝐿 𝐸𝑥𝐿 − 𝐸𝑥𝐼𝑁 − 𝐸𝑥𝐷 = 0

𝐸𝑥𝐷 = 𝑇0∆𝑠𝑔𝑒𝑛

𝐸𝑥 = −𝑇0 𝑠 − 𝑠0 + ℎ − ℎ0

HINV

T s hCOP

h

In reversible cycle, minimum amount of input work is required for a given rate of energy transfer (thermal) between two thermal reservoirs.

HINV

T sCOP

h

COPINV-> How many watts of input power to produce 1 W of cooling power

TH .ΔS is Isothermal compressor work

ΔH is the Expander output work


Carnot Refrigerator & Liquefier

Carnot Refrigerator

Δs=sg-sf= 4.83W/(g/s)

Δh=hg-hf= 20.4 W/(g/s)

wREV=1430W/(g/s)

COPINV=71 W/W

Carnot Liquefier Δs=sH-sf= 28 W/(g/s)

Δh=hH-hf= 1564 W/(g/s)

wREV=6823 W/(g/s)

WC/COPINV= 100 W/(g/s)

Refrigerator transfers heat energy from a low temperature reservoir to a higher temperature reservoir

Work in refrigerator is calculated based on the difference between entropy and enthalpy of saturated vapour and liquid

Liquefier transfers heat energy from over a large varying temperature span (decreasing as fluid being cooled) to a higher temperature reservoir

Work in Liquefier is calculated based on the difference between entropy and enthalpy of fluid at ambient temperature and saturated liquid

Carnot work to liquefy 1 g/s (30 l/h) at 1 atmsaturation condition is equivalent to that for 100 W of refrigeration


Heat Conduction in solids

Thermal Conductivity integrals of several materials [W/m]


Thermal Radiation

• Complex system involving three heat transfer processes

– QMLI= Qrad+ Qsol+ Qres

– With n reflective layers of equal emissivity, Qrad~ 1/(n+1)

– Due to parasitic contacts between layers, Qsol increases with layer density

– Qresdue to residual gas trapped between layers, scales as 1/n in molecular regime

– Non-linear behaviour requires layer-to-layer modeling

• In practice

– Typical data available from (abundant) literature

– Measure performance on test samples

Multi-layer Insulation



31/01/2020 IJAS-2020 VECC Kolkata

E401

E402

E403

E404

E405

E406

BUFFER

TANK

20 m3GN2

TO ATM.

DRYER

R

R

PURE H.P. CYLINDERSTORAGE

IMPURE H.P.CYLINDERSTORAGE

GAS BAG

LEAK / SYS. DISCHARGE /

BOIL OFF GAS FROM DEWAR

RECOVERYCOMP. 1

Gas bag

WarmExpander

ColdExpander

Turbo Mol. Pump

RotaryVacuum Pump

JTV 1COLD BOX

Purifier

A

LIQUID HELIUMDEWAR 1000L

LIQUID AIRDISCHARGE

A

JTV 2

RECOVERYCOMP. 2

ORM

PCV225

PCV229

CYCLECOMPRPCV223 LN2

DEWAR

23

12

3

45

6

7

8

9

S (entropy)

T (K

)

300 300

224 90

74 40

58 33

20 14

6.8 6.2

11 9

4.5 4.5

T-S diagram in liquefaction mode(Claude Cycle)

1.05 bar14 bar

5.4 bar

W/O LN2MODE

LN2MODE


Plate-fin Heat Exchanger & Turboexpander


Cryostat Cool Down & Warm-up

Cryostat cool down

0

50

100

150

200

250

300

29/12/04 31/12/04 02/01/05 04/01/05 06/01/05 08/01/05 10/01/05 12/01/05 14/01/05 16/01/05 18/01/05

Date (mm-dd-yy)

Tem

pera

ture

(K

)

T1

T2

T3

T4

JT Inlet T

Return T

Cool Dow n stopped for 118

hours due to non-availability

Cryostat warm up

0

50

100

150

200

250

300

350

1/3/06 3/3/06 5/3/06 7/3/06 9/3/06 11/3/06 13/3/06 15/3/06 17/3/06 19/3/06 21/3/06

Date ( mm/dd/yy)

Tem

pera

ture

(K

)

COIL TEMP T1

COIL TEMP T2

COIL TEMP T3

COIL TEMP T4

OUTLET TEMP T5

INLET TEMP T6

WARM HELIUM GAS HAS BEEN SENT

FROM THE HE-REFRIGERATOR


Problems faced and modifications proposed

• Malfunction of CLTS temperature sensors makes control erratic – replaced with Lakeshore make Cernox sensors

• Temperature distribution of the warm and cold turbine appeared to be not usual – Process Expert intervention

• RS-485 communication should be activated

• Expander operation not optimum when cryostat connected – expander control program modified with speed feedback and seven attenuators

• 400 KVA UPS was planned for preventing helium loss


Cold Box modification of Helial 50

Photos from top left

Cold Box lifting

Inside of cold box

Cernox sensor installation



Refrigeration Test 250W @ 4.5K 11/01/2007, without liquid nitrogen pre-cooling

29

Modifications with introduction of Helial 2000

• Introduction of a new refrigerator/liquefier of higher capacity - Helial 2000 in parallel with Helial50

Redundancy as the existing one is old

Additional capacity to cater more refrigeration load

LHe supply for new projects in cryogenics

• Provision of Subcooler

Reduction in flash-loss and increase in liquid yield

Reduction in pressure drop and return gas flow

• Interface of 2 refrigerators for parallel operation

• Selectivity of three screw compressors – 2 nos. for new

• For simultaneous operation pressure control in new ORS

• Use of same GHe HP and LP lines and put flanges for disconnection and reconnection if required


Capacity of Helial 2000 refrigerator

New RefrigeratorHelial 2000

Without LN2 pre-cooling (HP @ 14 bara) Flow rate- 82 g/sec

With LN2 pre-cooling

Liquefaction mode: 80 lph 176 lph

Refrigeration mode for 4.5K temp. level:

415 W 530 W(Designed)

Mixed mode at 4.5 K 360 W + 13 lph360 W + 25 lph (Designed)

360 W + 76 lph (Designed)

Cyclotron Connection switchable from one refrigerator to other almost seamlessly

Tube to tube connection inside the cold box using VBO coupling (O-ring) was avoided

Space constraints in nearby location – meticulously planned


Overall Cryogenic System including Cryopanel which improved Vacuum Level in the Beam Chamber

R

PURE H.P. CYLINDERSTORAGE

PCV225

PCV229

PCV223

CYCLE COMPRESSORS

BUFFER 60 m3 ORM 1 Charcoal &

Oil filters

PCV289

PCV280

PCV275

ORM 2 Charcoal &Oil filters

BUFFER 60 m3

BUFFER 20 m3

C1

C2

C3

E401

E402

E403

E404

E405

E406

WarmExpander

ColdExpander

JTV 1

Helial50 cold box250W @ 4.5K50 lit/hr

A

A

JTV 2

LN2 cooling

E401

E402

E403

E404

E405

E406

WarmExpander

ColdExpander

JTV 1

Helial2000 cold box415 W @ 4.5K85 lit/hr

A

A

JTV 2

LN2 cooling



DEWAR 60L

CRYO PUMP

CRYO PANELS

SCC CRYOSTAT

From CurrentLeads

CDS valve box

HX

DSTRIBUTION BOX SUB-COOLER

To LP

Current Leads

Schematic showing existing andNew liquefier together

Old Refrigerator New Refrigerator & Distribution box with Subcooler

Glimpses of Cryogenic System of VECC


Problems faced during commissioning

• Capacity test failed – 340 W @ 4.5K and 64 l/h

• Flow requirement higher suggested, Cv of JT and cold return valve enhanced with no effect

• Effectiveness of the first HX : prolonged temp. monitoring at inlet & outlet of CB – found OK

• Cold diversion from the LHe and cold gas return line at the side of CB interface 10.6g/s at 300K maximum

• Plug was modified by using Kel-F PCTFE material without much success – Vertical alignment is the problem

• Problem was fixed by addition of a flexible part in the vertical section to allow a free insert of the male part into the CB



Liquefaction vs. Refrigeration Load for Helial 2000 after modification

0 100 200 300 400

0

20

40

60

80 Liquefaction vs refrigeration

Linear FitL

iqu

efa

cti

on

ra

te l/h

Refrigeration load (W)

Sandip Pal, U. Panda, A. Mukherjee, T. Maiti, and R. Dey, Indian J. of Cryo., 37(1-4), 2012, pp. 122-127.R. Dey, Sandip Pal, et. al., Indian J. of Cryo., 36(1-4), 2012, pp. 103-107.


Cryostat Cool-down with Helial 2000

20/06/2010 04/07/2010 18/07/2010 01/08/2010

0

50

100

150

200

250

300

350

400

T1

T2

T3

T4Co

il T

em

p #

1, #

2, #

3 &

#4

(K

)

Date

Cool-down stopped

due to air ingress problem-100

-50

0

50

100

150

200

250

300

T5

T6

Inle

t &

Ou

tle

t te

mp

era

ture

(K

)

Cryostat JT

Closed


Cool Down Result in the year 2018

-20

0

20

40

60

80

100

120

0

50

100

150

200

250

300

29/08/2018 31/08/2018 02/09/2018 04/09/2018 06/09/2018 08/09/2018 10/09/2018 12/09/2018

Leve

l (%

)

Tem

pe

ratu

re (

K)

Date

Cryostat Temp. T1, K




Cryostat Outlet Temp. T5, K

Cryostat Inlet Temp. T6, K

Dewar Level %

Cryostat Lower Level %

Cryostat Upper Level %

Stopped plant for compressor belt change during 9:00 hrs to 17:00 hrs

EPICS based control system

MEDM

LAN

IOC

Helial 2000

Helial 50

Overall Management

Channel Archiver for database

OPIs


MEDM Overview Screen of the Cryogenic System

U Panda, Sandip Pal, R Dey, T Bhattacharjee, A Mandal, Control System of Cryogenic Plant for Superconducting Cyclotron at VECC, Proceedings of CYCLOTRONS 2010, MOPCP008, Lanzhou, China, 6-10 September, pp 53-55.



Development and Testing of Variable Temperature Insert (VTI)

41


Results of Cryogenic Temperature Sensor Calibration using VTI

0 200 400 600 800 1000

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4 Calculated Temperature from Pressure

Polynomial Fit

Tem

pera

ture

co

rresp

on

din

g p

ressu

re (

K)

Saturation Vapour Pressure (mbar)

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

Temperature wrt Si Diode Voltage

Polynomial FitT

em

pera

ture

wrt

Si

Dio

de V

olt

ag

e (

K)

Variation of Temperature calculated and measured at different pressures

0 50 100 150 200 250 300 350

0

1000

2000

3000

4000

5000

6000

7000

0

500

1000

1500

2000

2500

3000 Sensor #1 Measured

Sensor #1 Calibrated

Ce

rno

x C

X-1

05

0 R

esis

tan

ce

(O

hm

s)

Temperature (K)

Sensor #2 Measured

Sensor #2 Calibrated

Error 4.2K: ±0.02K77K: ±0.25 K300K: ±0.62 K

Stability: 0.02 K

Sandip Pal, R Kar, A Mandal, A Das, S Saha, “Development of an experimental variable temperature set-up for a temperature range from 2.2 K to 325 K for cost-effective temperature sensor calibration,” Measurement Science and Technology 2017, 28 (5), 055013

42

Development of moisture Spectrometer

Pressur

e

GaugeElectronic

Module

Laser

Source

Beam

Splitte

r

Absorption

Cell

Optical

Window

Slit

Detector

with

Preamplifie

r

Detector

with

Preamplifie

r

Measureme

nt Beam

Referen

ce Beam

Mirror

Laser

Driver

Low-pass

Filter

I-V

converter 14-bit

DAC

DDS Selection of

Ramp & Sine

Gain control

16-bit

MDAC

16-bit 10

MSps ADC

LP

filter

Splitter

Detectors

I-V

Instrumentation

Amplifier

ADC

Driver S

R

D

Absorption

Cell

FPGA board

PSD

Moving

Average

NI-6534

Ethernet

Sandip Pal, Ananda Das, Sushanta Nandy, Ranjan Kar, and Jaharlal Ghosh, “Development of a near-infrared tuneable diode laser absorption spectrometer for trace moisture measurements in helium gas,” Review of Scientific Instruments, 90, 103105 (2019); https://doi.org/10.1063/1.5113968.


PurifierTechnical Specification:• Flow Rate: 20 nm3/hr• Operating pressure: 150 bar• Min. adsorption pressure: 120 bar• Operating temperature: 77K i.e. LN2

temperature• Max. input gas impurity: 40% air impurities• Output gas purity: 99.995% or Grade 4.5 helium i.e. total air impurity < 50 ppm • Run time: 6 hours• Adsorbent: Coconut shell granular activated charcoal• Regeneration type: Thermal swing regeneration with evacuation

BRNS Project with NIT Rourkella31/01/2020 IJAS-2020 VECC Kolkata 44

31/01/2020

Development of Helium Purifier

Sample No.

H2O (vpm)

N2

(vpm)O2

(vpm)Total

impurities

(vpm)

1 1.70 2.10 0.20 4

2 2.30 1.50 0.10 3.9

3 1.40 1.40 0.30 3.1

4 1.50 2.80 0.30 4.6

Analysis Results for input of 5% Impure gas

In collaboration with NIT Rourkella

IJAS-2020 VECC Kolkata 45

Critical current density of common LTC Superconductors


Isotope Separator On Line

RIB

target 238U

fission products

Ion Source

Post-accelerator

Radioactive Ion Beam

E-Linace- g

tantalumconverter

50 MeV, 100 kW cw Superconducting Electron LinacBased on 1.3 GHz , 2K, SRF technology

Scheme of photo-fission production of RIB in ANURIB

Injector to be tested at VECC Salt Lake Campus


E-Linac Cryomodule : SchematicCryo-insert for converting 4K Lhe to 2K

•Suspension from lid

•Cold mass supported by strong- back

•Cryogenic insert (removable from cryomodule in situ) includes

o 4K phase separator,

o 2.5g/s heat exchanger

o JT expansion valve to produce 2K liquid,

o 4K cooldown valve and

o 4K thermal intercept ckt. in a thermal siphon configuration; insert LN2 cooled thermal shield; 4K circuit for intercepts (RF couplers, beam pipe)

• Warm and cold mu-metal

• MLI for 4K & 2K cold mass


The ACM top Assembly and ICM


Estimated Heat Loads of E-linac Cryogenic System


Liquid Helium plant for e-Linac at VECC

Linde LR280 With LN2 Without LN2

Refrigeration @ 4.5KGuaranteed / Actual

680 W690 W

540 W569 W

Mixed ModeGuaranteed / Actual

205W & 235 l/h205 W & 293 l/h

Liquefaction @ 1.3 bar aGuaranteed / Actual

325 l/h375 l/h

115 l/h126.5 l/h


elinacCryomodules

Subatmospheric

Pumping system Compressor

He Dewar

Cold Box“Clean” HeliumStorage Tank

OR/GMS,

Dryer,

Purifier

“Dirty” HeliumStorage Tank

Purity monitoring(control) System

Simplified block diagram for e-Linac He Cryogenic System


53

ColdBox

He cleanbuffer tank

Sub-atm Pump

MAIN Compr.

CryomodulesDewar

LN2tank

Purif./ Recov.Compr.

Purifier He Heater

N2 Heat Exng

CompressorBuilding

He dirty buffer tank

He Heat Exng

recovery

cooldown

coo

ldo

wn

cleaning

dumping

E-linac Cryogenic System Block Diagram


Liquid Helium (LHe) and Sub-atmospheric (SA) Transfer Line -Schematic

LHe

DewarCold Box

ICM

Heat

Exchanger

Hx

LHe Supply Transfer line

LHe Return Transfer line

SA Return line

SA Return line

To compressor room Keep-cold

TEST AREA

Bellow joint

Control Valve

Stringer

LHe Supply/ Return

Field joint

Sub-atmospheric

Return line

26th NSCS-2017, VECC, Kolkata

LHe

Dewar

Cold

Box

ICM

TE

ST

AR

EA

LN2

Out

LN2 In

LN2 to

shield

Compressor

room

Keep

cold

Liquid Nitrogen Transfer Line Schematic

LN2

storag

e tank

Manifold-2

LN2 to shield

Manifold-3

Manifold-1

To RIB

annex

To HR Cave 1

LN2 from

shield

LN2 from

shield

Ambient

vaporizer

Vent

Purifier Cry

o-

ad

sorb

ers

Vent

Shut off valve

Control Valve

VJLHe supply

VJLHe return

VJLN2 supply

VJLN2 return

VJGN2 return

GN2 vent

Field joint

To

compresso

r room

Cross

LN2

Dewar/

Phase

separator

LN2

Dewar/

Phase

separator

SCADA for Linde Liquefier



Conclusion

• Our work should be critically looked,

• No compromise in system development,

• Culture is important

Thank You


Documents

Cryogenics for particle Accelerators · magnetic field - B < 2 Tesla –Iron Yoke and normal magnet B < 5.5 Tesla –Superconducting magnet of Nb-Ti wire at 4.2 K B ~ 8-10 Tesla -