Ramesh Gupta BNL€¦ · Ramesh Gupta, BNL Radiation Studies for HTS Magnets Fusion and Accelerator...

Superconducting Magnet Division

Ramesh Gupta, BNL Radiation Studies for HTS Magnets Fusion and Accelerator Magnet Workshop, Italy, May 26-29, 2008 1

Radiation Studies for HTS Magnets

Ramesh GuptaBNL

http://www.bnl.gov/magnets/staff/gupta



Motivation

• Radiation damaged studies are being carried for the proposed RIA (Rare Isotope Accelerator), now morphed to FRIB (Facility for Rare Isotope Beams).• Critical quadrupoles in Fragment Separator region are exposed to unprecedented level of radiation (~20 MGy/year) and heat loads (~10 kW/m, 15 kW in first quad itself). • CLAIM: HTS magnets can withstand and remove these radiation and heat loads economically. • A comprehensive conductor and magnet R&D program was carried out to demonstrate above.• The results of this successful program may have far reaching impact on many future proposals.

X(c

m)

Quad Triplet

1.3 meter

Courtesy: Al Zeller, NSCL

400

kW b

eam

from

LIN

AC

(to

Fra

gmen

t Sep

arat

or)



Radiation Damage Studies of HTS (YBCO, Bi2223 and Bi2212)

• BNL and NSCL (Zeller) are collaborating in radiation damage studies on HTS and on determining the impact of it in the performance of actual magnets.

• First set of radiation damage studies on Bi2223 was carried out by Al Zeller at LBL Cyclotron (paper published).

• More recent studies on YBCO, Bi2223 and Bi2212 are being carried out by George Greene and Bill Sampson at BLIP.

• Test results and analysis of radiation damage on YBCO will be briefly presented. YBCO samples were provided by SuperPower and American Superconductor Corporation.



Key Steps of Radiation Damage Experiment(Courtesy George Greene and Bill Sampson)

190

1

890.00

10,000.00

20,000.00

30,000.00

40,000.00

50,000.00

60,000.00

arbitrary intensity

scale

mm below tab

E towards tab

Foil Irradiation Surface Plot

50,000.00-60,000.0040,000.00-50,000.0030,000.00-40,000.0020,000.00-30,000.0010,000.00-20,000.000.00-10,000.00

Tab ->(Up) East

West

Down

142 MeV, 100 μAprotons



Radiation Damage Studies at BLIP

The Brookhaven Linac Isotope Producer (BLIP) consists of a linear accelerator, beam line and target area to deliver protons up to 200 MeVenergy and 145 µA intensity for isotope production. It generally operates parasitically with the BNL high energy and nuclear physics programs.

From a BNL Report (11/14/01)



Change in Critical Current (Ic) of YBCO Due to a Large Irradiation

Radiation Damage Studies on YBCO by 142 MeV Protons by G. Greene and W. Sampson at BNL (2007-2008)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

0 25 50 75 100 125

Radiation Dose (μA.Hours)

I c (Ir

radi

ated

) / I c

(Ori

gina

l)

SuperPower Sample#1SuperPower Sample#2SuperPower AverageASC Sample#1ASC Sample#2ASC Average

100 μA.hr dose is ~ 3.4 X 1017 protons/cm2 (current and dose scale linearly)

Ic Measurements at 77 K, self field

Ic of all original (before irradiation) was ~100 Amp

Ramesh Gupta, BNL 3/2008



~ 1.7 X 1017

protons/cm2

Ic (1μV/cm) as a function of temperature

T (kelvin)

I c(A

) @

1μV/

cm

~ 3.4 X 1017

protons/cm2

Change in Critical Temperature (Tc) of YBCO Due to a Large Irradiation

Before Irradiation

Note:Radiation damage has impact on Tc, in addition to that on Ic.

One way to recover the loss in performance due to radiation damage is to operate magnet at a lower temperature – something that is not possible in conventional LTS magnets.

Results will be formally

presented at ASC2008.



Impact of Irradiation on Magnet

• The maximum dose was 3.4 X 1017 proton per sec 100 μA.hr.• As per Al Zeller, displacement per atom (dpa) per proton is ~9.6 X 10-20. This gives ~0.033 dpa at 100 μA.hr.

Bottom line: • Ic performance of YBCO will drop ~10% after 30 years operation.• This is pretty acceptable !!!

Caveat:Above is based on 77 K, no applied field.To be completely sure, examine it at 50 K and 3 T (or whatever the operating parameters may be).

• It appears that YBCO is at least as much radiation tolerant as Nb3Sn is (Al Zeller).

Radiation Damage Studies on YBCO by 142 MeV Protons by G. Greene and W. Sampson at BNL (2007-2008)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

0 25 50 75 100 125

Radiation Dose (μA.Hours)

I c (Ir

radi

ated

) / I c

(Ori

gina

l)

SuperPower Sample#1SuperPower Sample#2SuperPower AverageASC Sample#1ASC Sample#2ASC Average

100 μA.hr dose is ~ 3.4 X 1017 protons/cm2 (current and dose scale linearly)

Ic Measurements at 77 K, self field

Ic of all original (before irradiation) was ~100 Amp

Ramesh Gupta, BNL 3/2008



Stainless Steel Insulation in HTS Coils

Radiation damage to insulation is another major issue for magnets in high radiation area.

SS Tape

HTS Tape

• In FRIB/RIA magnets SS tape, rather than the kapton tape, is used as insulator.

• Relatively to superconductor, stainless steel is a good insulator.

• The major advantage of stainless steel is that being metal, it is highly radiation resistant.

RIA/FRIB coil being wound with HTS and stainless steel



RIA/FRIB HTS Quad Models for High Radiation, High Energy Deposition (~15 kW) Magnets

Warm iron R&D quadrupole with twenty four coils in two cryostats

1.3 meter

Mirror Iron

Return Yoke Iron Pole

HTS Coils in Structure

War

m ir

on m

irro

rC

old

iron

mir

ror

mod

el



Setup for Energy Deposition Experiments

Copper sheets, etc. between HTS coils for other conduction cooling experiments

Stainless steel tape heaters between coils for energy deposition experiments

Tests must demonstrate an stable operation of HTS magnet at 30 Kelvin with a huge 25 W (5mW/cm3 or 5kW/m3) heat load on coils.



15

17

19

21

23

25

27

29

31

33

0 5 10 15 20 25 30 35 40

Time (min)

Tem

p (K

)

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

Volta

ge G

radi

ent (

V/cm

)

Temperature in various thermometers between HTS coils

Voltage gradient across the whole coil package

Simulated Energy Deposition Experiment at the Operating Condition (Environment)

Goal is to demonstrate that the magnet can operate in a stable fashion at the expected heat loads (5mW/cm3 or 5kW/m3 or 25 W on 12 short HTS coils) at the design temperature (~30 K) with some margin oncurrent (@140 A, design current is 125 A).

We use 0.1 μV/cm as the definition of Ic.

Temperature differences may be partly real and partly calibration mis-match.

As such HTS can tolerate such temp variations with small margin.

Stable operation for ~40 minutes

Voltage spikes are related to the noise



SUMMARY

• Useful, systematic, high dose, radiation damage experiments have been performed at BLIP. The setup is available for other future studies.

• Based on 77 K, zero field measurements, it has been demonstrated that HTS can survive high radiation doses as present in FRIB (or RIA).

• It has been also been shown that HTS can remove very high heat loads at elevated temperature and can operate in an stable fashion.

• Surprisingly, it was also found that in this application, the proposed HTS magnet option was cheaper (Zeller, PAC’05) than the radiation resistant water-cooled copper design (which was giving a lower performance).

Ramesh Gupta BNL€¦ · Ramesh Gupta, BNL Radiation Studies for HTS Magnets Fusion and Accelerator...

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