1. 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, MP3 meeting 15/7/2009 RRR

2. What is RRR (Residual Resistance Ratio)? Definition:  (290 K)/  (4 K) take care: many variants exist, such as  (300K)/  (4K),  (273K)/  (4K) ….  =1.7e -8 /RRR + 1/(c 1 /T 5 +c 2 /T 3 +c 3 /T) + f(RRR,B) The residual resistivity (for T  0, 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. Arjan Verweij, TE-MPE, MP3 meeting 15/7/2009

4. 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: RRR meas : 210-220 Minutes EEWG 1/6/2003: early production: RRR about 100, now RRR>200 Measurement D. Richter on short samples in 2009 4 MB samples: 223-276 4 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) Arjan Verweij, TE-MPE, MP3 meeting 15/7/2009

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

6. RRR has strong effect on stability RRR_busRRR_cableI_safe (adiab.) 801006433 801606715 802407088 100 6683 1001607110 1002407411 1201007055 1201607406 1202407801 1601007318 160 7841 1602408248 RQ joint, tau=15 s, no helium cooling, 40 mm void Accuracy in RRR of about 20% is sufficient for calculation work Arjan Verweij, TE-MPE, MP3 meeting 15/7/2009

7. Know-how of RRR could improve joint analysis at 80 K T [K] RRR_busR 30m [uOhm]  R/R 30m R of typical silent killer (R SK ) [uOhm] R SK /  R 2901001788 0.005505.6 2902001779 80100249 0.0377.0 (assuming RRR SK =100)0.78 80200240 2010019.4 0.610.54 (assuming RRR SK =100)0.06 2020010.3 Neglecting temperature errors Accuracy in RRR of 10% would give R SK /  R  7 at 80 K Arjan Verweij, TE-MPE, MP3 meeting 15/7/2009

8. T [K] RRR  T [K] Neg RRR error Pos. RRR error Average RRR error [%] 251001-3.24.03.6 251002-5.98.97.4 251003-8.115.011.5 252001-12.416.27.1 252002-21.938.215.0 252003-29.468.824.6 201001-1.51.81.6 201002-2.74.03.4 201003-3.66.85.2 202001-5.77.33.3 202002-10.216.66.7 202003-13.728.710.6 151001-0.50.70.6 151002-0.91.51.2 151003-1.22.51.9 152001-2.02.61.1 152002-3.56.02.4 152003-4.510.33.7 Arjan Verweij, TE-MPE, MP3 meeting 15/7/2009

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