# Presentation: 907263

## React & Wind test resultsanalysis and next steps

- OUTLINE
-  Racetrack goals and description
-  HFDB-03 tests results
-  Preliminary analysis
-  Plan for the future

- Giorgio Ambrosio

## Areas of study

**Strands:**** study the Ic degradation vs. bending strain in different wires**
**Cables:**** measure degradation in cable**
**Racetrack coils:**** study conductor performances in magnet environment (quench performances, training, effect of temperature and ramp rate, quench propagation study)**
**Ten-stacks:**** measure thermal contraction coefficient, elastic modulus,**** **
**Inter-strand resistance**** measurements**

- June 3 - 4, 2003

## HFDB-03

- Cable: 41 strands,  = 0.7 mm,
- Wire by OST (MJR)
- Cabling at LBNL

**	****GOALS:**
**Reproduce HFDB-02 results**
**78% ssl at 12675 A  (7.7 T)**
**Improve performance and/or have a better understanding of the causes of limits**

| Maximum field (T)  | 10 |
| --- | --- |
| Current at ss (A) | 16527 |
| Fy at ss (MN/m) | 1.44 |
| Inductance (mH) | 0.29 |
| Energy at ss (kJ) | 40 |

_***HFDB-03***_

- Field distribution in the coil at 16000 A

- June 3 - 4, 2003

## Instrumentation

_***Instrumentation***_

- Voltage taps and
- Temperature sensors

-   44 voltage taps
-    7 temperature sensors
-    3 spot heaters
-    4 quench heaters
-   18 instrumented bolts/bullets
-    2 capacitance gauges

- June 3 - 4, 2003

## FE analysis – Test comparison

- All loads in N

**Preload lower then nominal (because of bending)**
**Slightly larger losses during cooldown **
**No preload on the main bolts after cooldown from slope of ********l vs I****2**
**NO load increase on bullets during excitation**

- June 3 - 4, 2003

## Quench history

- * 78% taking into account coil temperature > 5 K

- June 3 - 4, 2003

## Quench history HFDB-02 and -03

**Quench current at 20 A/s**
**In HFDB-02:**
**10914 – 12038 A**
**In HFDB-03:**
**9520 – 10824 A**

- June 3 - 4, 2003

## Typical quench

**Almost all quenches started from the same location: 1****st****  turn of the top coil**
**Very fast propagation to all close-by segments (< 3 ms)**

- June 3 - 4, 2003

## Voltage rise in typical quench

-  Quench at 10 kA
-  12-turn segment (18.7 m)
-  Resistance at cold 9 m
-  R = 7.5 m in < 20 ms
-  RRR ~ 5
-  V = 780 m/s ?!?

- June 3 - 4, 2003

## Ramp rate dependence

**	****Higher Iq at higher ramp rates**
**Same behavior as in HFDB02 but the max is at 300 A/s instead of 75 A/s**
**Coils were warmer at high ramp rates **
**    ****6-7 K at 300 A/s**

**“****NO ramp rate dependence in BNL **
**10-turn coils made with ITER strand”**
*R. Gupta personal communication*

- June 3 - 4, 2003

## Temperature dependence

**	****No gain in Iq at lower temperature**
**In HFDB-02 we saw a small decrease of Iq vs. temperture**

- June 3 - 4, 2003

## Special ramps

**Best quench current (12536 A) ramping at 300 A/s **
**after fast pre-cycle (0 – 8000 – 0 A) at 500 A/s**
**2****nd**** best quench current (12461 A) ramping up at 300 A/s**
**after several cycles (0 – 6000 – 0 A) at 600 A/s **
**coil temperature was between 7 and 9 K during cycles**
**... ****other pre-cycles gave mixed results   **

- June 3 - 4, 2003

## Temperature margin in the innermost turns

**Current value**
**I = 5, 7, 9, 11 kA**
**Spot heater was connected to a DC power supply**
**Heater current was raised very slowly until quench **
**Temperature was recorded by adjacent sensor**

- June 3 - 4, 2003

## Other studies

**Spot heater studies**
**Quench propagation velocities**
**Quench heater studies**
**Minimum voltage to quench at varying I/Ic**
**Delay time at varying I/Ic and voltage**

- June 3 - 4, 2003

## Preliminary analysis

**Multipole quenches / fast propagation:**
**Simultaneous start of different segments**
**Time of flight: ~ 100 – 130 m/s**
**Resistance rise: ~ 780 m/s ?!?**
**In case of spot heater induced quenches it’s slower but still very high**
**Unconventional ramp-rate and temperature dependence:**
**Higher Iq at 300 than 20 A/s **
**Best performance with “warm” coils (T ******** 6-7 K at 300 A/s)**
**Temperature margin measurement:**
**Tsensor > 9 K at 11000 A**
**“****Snappy events”:**
**2-5 each ramp**
**Same shape of LBL “slow FFC (fast flux change)”****†**** **

- † A.Lietzke et al.,“*RD3c Fast Flux Change Test Results*” RD3c Test Report

- June 3 - 4, 2003

## Mechanical / Conductor  instability

**“****Snappy events”**
**Flux jumps according to LBL****†**
**Short sample tests show quenches well below the Ic at low field**

**2 VTs lost in the same location (bottom and top coil)**
**NO preload on the main bolts at cold**

- June 3 - 4, 2003

## FNAL- LBNL racetrack comparison

**LBL racetracks go to higher fields ******** operate at lower J**
**But the current/wire of RT1 is the same as our Racetracks**
**There is NO iron in our Racetracks**
**But there wasn’t much in RT1**
**Our Racetracks have only ONE layer**
**But the quench location is not the one you would expect if this was the problem (i.e. it should be in the center of the coil where the strands go from 0 to Max field)**
**We use the React-and-Wind technology**
**We have a much higher inter-strand resistance **
**Shown by the big difference of ramp-rate dependence**
**This is a BIG DIFFERENCE and so ....**

* ****  **is poor CABLE STABILITY a/the problem?*

**May be consistent with BNL results:**
**Promising results with ITER wire, bad results with high-Jc wire**

- June 3 - 4, 2003

## 2nd thermal cycle

**In the 2****nd**** thermal cycle we will:**
**Increase pre-stress (computed from data of 1****st**** cycle)**
**Instrument both bullets on some end-shoes**
**Measure AC-losses (not done during 1****st**** cycle)**
**Study “special pre-cycles”**
**In order to:**
**Study performance under higher pre-stress and compare results with 1****st**** thermal cycle**
**Have a better understanding of load on the end-shoes**
**Estimate inter-strand resistance**
**Obtain more info about instability sources**

- June 3 - 4, 2003

## Plans for the future

***GOAL:***
***    ******Develop Nb******3******Sn React-and-Wind technology in order to use it in Common Coil magnet***** **
**	****Short term goal is to understand and fix the source of present limits by: **
**New Racetrack**
**Short fabrication time**
**Better control of the mechanical structure**
- Measurement and control of inter-strand resistance
- Measurement of bending degradation of PIT wires

- June 3 - 4, 2003

## New Racetrack

**	****New features:**
**Coils will be wound and impregnated separately**
**Pre-stress will be applied separately**
****** ****Better control of the mechanical structure**
**Coils could be changed and reconnected**
****** ****Allowing test of one coil at a time**
**Variable number of turns (for expensive conductor)**
**Base-coil fabricated with Wind-and-React technology **
**Fabrication time for one coil: 3 weeks**
**Magnet assembly: 2-3 weeks**
****** ****Ready for test in 7 weeks**

- June 3 - 4, 2003

## Program

**	****The program will develop according to the results, the baseline plan is:**** **
**Complete analysis of HFDB-03 test results**
**Develop new Racetrack**
**Study inter-strand resistance in cables for React-&-Wind **
**develop techniques to control it or alternative to use of synthetic oil**
**Study bending degradation of PIT wires (and RRP)**
**Fabricate base-coil (W&R) and 1****st**** coil with **
**PIT conductor **
**and/or controlled inter-strand resistance**

- June 3 - 4, 2003

## APPENDIX

- June 3 - 4, 2003

## HFDB-02 mechanical structure

- F

- E

_***HFDB-02 ***__***mechanical structure***_

- June 3 - 4, 2003

## Short sample limit

**measured J****c**** virgin strand: 1866 A/mm****2 ****@ 12T 4.2K**
**measured cabling degradation: ****2%**
**measured bending degradation @ 10T 4.2K**
**6% (********b**** = 0.22%)  ****15%**** (********b**** = 0.47%)**

-  estimated degradation: **17 %**
-  short sample limit:  16870 A @ 10.2T 4.5K
- NOTE: effect of the bending degradation on the load line:  **5%**

- June 3 - 4, 2003

## HFDB-01

- June 3 - 4, 2003