Proposal for RRR measurement in S-12 at 15-25 K MP3 meeting, 15 July 2009, Arjan Verweij With input from Bob Flora and Udo Wagner Arjan Verweij, TE-MPE,

Proposal for RRR measurement in S-12 at 15-25 KMP3 meeting, 15 July 2009, Arjan Verweij

With input from Bob Flora and Udo Wagner

Arjan Verweij, TE-MPE, MP3 meeting 15/7/2009

RRR

What is RRR (Residual Resistance Ratio)?

Definition: r(290 K)/r(4 K) take care: many variants exist, such as r(300K)/r(4K), r(273K)/r(4K) ….

r=1.7e-8/RRR + 1/(c1/T5+c2/T3+c3/T) + f(RRR,B)

The residual resistivity (for T0, B=0) is due to electron scattering and depends on microstructure features (impurities, grain boundaries, dislocations, …).

Typical RRR-value for Cu is 100. Mechanical work and heat treatments affect the RRR. High purity copper can have RRR as high as 1000. Small contents of various components (Fe, Ag, Al, Si, …) reduce the RRR.


4.E-11

4.E-10

4.E-09

4.E-08

3 30 300

rho

[Oh

m m

]

Temperature [K]

80

120

160

200

300


What do we know about the RRR of the bus?

Specification (IT-2882): length: 34 m -0, +0.3 m. RRR>100 to be measured on 3 samples per batch.

MT-17 paper: RRRmeas: 210-220

Minutes EEWG 1/6/2003: early production: RRR about 100, now RRR>200

Measurement D. Richter on short samples in 20094 MB samples: 223-2764 MQ samples: 237-299

Measurement on RB segments in R2 (with biddle):average=117, sigma=11, min=89, max=161(measurement accuracy might be an issue)


Why is it important to know the RRR ?

1. RRR has strong effect on stability

2. Knowing the RRR could improve joint analysis at 80 K

3. RRR affects quench propagation speed in the bus, and could therefore influence the magnet-to-magnet quench propagation (only at higher currents).

0

1000

2000

3000

4000

5000

6000

3 30 300

Ther

mal

cond

ucti

vity

[W /

(m K

)]

Temperature [K]

80120160200300


RRR has strong effect on stability

RRR_bus RRR_cable I_safe (adiab.)

80 100 6433

80 160 6715

80 240 7088

100 100 6683

100 160 7110

100 240 7411

120 100 7055

120 160 7406

120 240 7801

160 100 7318

160 160 7841

160 240 8248

RQ joint, tau=15 s, no helium cooling, 40 mm void

Accuracy in RRR of about 20% is sufficient for calculation work


Know-how of RRR could improve joint analysis at 80 K

T[K]

RRR_bus R30m

[uOhm]DR/R30m R of typical silent

killer (RSK)[uOhm]

RSK/DR

290 100 17880.005 50 5.6

290 200 1779

80 100 2490.037 7.0 (assuming RRRSK=100) 0.78

80 200 240

20 100 19.40.61 0.54 (assuming RRRSK=100) 0.06

20 200 10.3

Neglecting temperature errors

Accuracy in RRR of 10% would give RSK/DR7 at 80 K


T[K]

RRR DT[K]

Neg RRR error

Pos. RRR error

Average RRR error[%]

25 100 1 -3.2 4.0 3.6

25 100 2 -5.9 8.9 7.4

25 100 3 -8.1 15.0 11.5

25 200 1 -12.4 16.2 7.1

25 200 2 -21.9 38.2 15.0

25 200 3 -29.4 68.8 24.6

20 100 1 -1.5 1.8 1.6

20 100 2 -2.7 4.0 3.4

20 100 3 -3.6 6.8 5.2

20 200 1 -5.7 7.3 3.3

20 200 2 -10.2 16.6 6.7

20 200 3 -13.7 28.7 10.6

15 100 1 -0.5 0.7 0.6

15 100 2 -0.9 1.5 1.2

15 100 3 -1.2 2.5 1.9

15 200 1 -2.0 2.6 1.1

15 200 2 -3.5 6.0 2.4

15 200 3 -4.5 10.3 3.7


Proposal for S12

Setting temperature: 20±1 K.

Temp. stabilisation until difference between neigbouring temp. probes <2-3 K (1-2 days?).

Measurement of M1, M2, M3 lines with biddle (resolution 1 uOhm!!). Expected: 1-2 days.

Measurement with accurate DVM (Keithley) on a few segments to validate the results.

After analysis, we have to discuss:- if measurements at another temp. are needed (probably not)- if measurements in other sectors are useful (YES!!)- if measurement accuracy is sufficient


Documents

Proposal for RRR measurement in S-12 at 15-25 K MP3 meeting, 15 July 2009, Arjan Verweij With input from Bob Flora and Udo Wagner Arjan Verweij, TE-MPE,