1. Rotation Target R and D of ILC E-driven source
ferromagnetic
fluid seal
air
vacuum
T. Omori (KEK), 27-June-2017
2017 Americas Workshop on Linear Colliders
AWLC17
June 26-30, 2017, SLAC, Menlo Park, CA

2. Target
Positron
Electron
W-Re 14mm thick.
5 m/s tangential speed rotation (225 rpm, 0.5m diameter) in vacuum.
Water cooling through channel.
Vacuum seal with ferro-fluid.

3. R/D of the Slow Rotation Target of the Conventional e+ Source
Today’s Talk
R/D of the Slow Rotation Target
of the Conventional e+ Source
for ILC
• Target R/D (1): Heat&Stress Simulations, and Radiation Test
• Target R/D (2): Vacuum Test of the Prototype
• Summary

4. Heat&Stress Simulations
and
Radiation Test

5. Simulation : target stress and cooling
Pulse#02 225rpm
Pulse beam analysis: step 2
20 trains (pulses) in 63 ms
Temp.Max.; 356.0℃
Max-Stress (Von-Mises): 470 MPa
Stress: OK
Cooling: OK
Max-Stress is as same as that of SLC target. SLC target worked in 3-4 years.
Number of hit / Year.mm
NILC = NSLC/10
　Fatigue: ILC is 10 times better than SLC
Nb = 2600
Simulated by Rigaku
Cooling water: 60 l /min

6. TEST: Radiation Tolerance
FY2014
Takasaki Advanced Radiation Research Institute, JAEA
November 2014
10-Nov-2014

7. TEST: Radiation Tolerance
November 2014
More systematic study for CN oil
FY2014
Dose [MGy]
Viscosity
Viscosity as a function of dose
4.7 MGy
The seal dosed 4.7 MGy (3 ILC year) is examined with Ar purged chamber.
Rotation : rpm.
No leak was found.

8. Conventional (E-driven): Target
T. Omori

9. Vacuum Test of
the Prototpe

10. Prototype of the Rotation Target (E-driven)
Central Part
hollow shaft
motor
baring
ferrofluid seal
vacuum chamber
disk
• d= 500 mm
• wait ~ 70 kg
• no water
channel
finished in FY2015

11. Prototype: Central Part
hollow shaft
motor
bearings
ferrofluid seal
water seal
water outlet
water inlet
finished in March 2016

12. Central Part Prototype Vacuum Test
Feb/2017
Central Part Prototype: Funded by KEK
Vacuum Test: Funded mostly by Hiroshima Univ.

13. Central Part Prototype Vacuum Test
Feb/2017
Vacuum
chamber
Ion pump
100 litter/sec
Central part
prototype
Central Part Prototype: Funded by KEK
Vacuum Test: Funded mostly by Hiroshima Univ.

14. Central Part Prototype Vacuum Test Facts and What happened (1)
• Ion pump　100 litter/sec.
• Rotation at 225 rpm (design value).
• We started the experiment on February 9th.

15. Central Part Prototype Vacuum Test
Log (Pressure) [Pa]
9/Feb /Feb /Feb 　 2/Mar /Mar /Mar 23/Mar
Date
225 rpm
(design value)
1x10-5
3x10-6
4x10-6
2x10-5
5x10-6
The test started on February 9th with continuous rotation at 225 rpm
3x10-6 Pa
The vacuum test started on February 9th with continuous rotation at 225 rpm (design value). The vacuum level seems to be reasonable in comparison with the expectation. The vacuum level is as good as the ILC TDR requirement. It seems promising. But the prototype has no disk. We will make further study.

16. Central Part Prototype Vacuum Test
225 rpm
February/13 – March/28
Pressure [Pa] x10-6
Note: Linear scale
Date
13/Feb /Feb /Mar /Mar /Mar /Apr
3x10-6 Pa 7 7 6 6 5 5 4 4 3 3
225 rpm

17. Central Part Prototype Vacuum Test Facts and What happened (1)
• Ion pump　100 litter/sec.
• Rotation at 225 rpm (design value).
• We started the experiment on February 9th.
• Vacuum level went good monotonically.
• And reached ~ 3x10-6 Pa at the end of March.

18. Central Part Prototype Vacuum Test
March/28 – Apr/09
225 rpm 9 7
Pressure [Pa] x10-6
Note: Linear scale 5
3x10-6 Pa 3 1
28/Mar /Apr /Apr /Apr /May /May
Date
225 rpm

19. Central Part Prototype Vacuum Test Facts and What happened (1)
• Ion pump　100 litter/sec.
• Rotation at 225 rpm (design value).
• We started the experiment on February 9th.
• Vacuum level went good monotonically.
• And reached ~ 3x10-6 Pa at the end of March.
• Vacuum level was stable at ~ 3x10-6 until April 10th.

20. Central Part Prototype Vacuum Test
March/28 – Apr/09
225 rpm 9 7
Pressure [Pa] x10-6
Note: Linear scale 5
3x10-6 Pa 3 1
28/Mar /Apr /Apr /Apr /May /May
Date
225 rpm

21. Central Part Prototype Vacuum Test
Small spikes (x1.5 – x 2) were obsreved
March/28 – May/09
225 rpm 9 x2
April 10th 7
Pressure [Pa] x10-6
Note: Linear scale
x1.5 5
4x10-6 Pa
3x10-6 Pa 3 1
28/Mar /Apr /Apr /Apr /May /May
Date
225 rpm

22. Central Part Prototype Vacuum Test Facts and What happened (1)
• Ion pump　100 litter/sec.
• Rotation at 225 rpm (value).
• We started the experiment on February 9th.
• Vacuum level went good monotonically.
• And reached ~ 3x10-6 Pa at the end of March.
• Vacuum level was stable at ~ 3x10-6 until April 10th.
• Then, we observed small spikes.
- High of a spike ~x1.5.

23. Same weight as real wheel.
Prototype test (not full size yet) of the unduraor target at LLNL was not fully successful ( )
Same weight as real wheel.
Smaller diameter.
2000 rpm
Note: Logarithmic scale
Note: Torr

24. Central Part Prototype Vacuum Test Facts and What happened (1)
• Ion pump　100 litter/sec.
• Rotation at 225 rpm (design value).
• We started the experiment on February 9th.
• Vacuum level went good monotonically.
• And reached ~ 3x10-6 Pa at the end of March.
• Vacuum level was stable at ~ 3x10-6 until April 10th.
• Then, we observed small spikes.
- High of a spike ~x1.5.
(cf. Undulator target at LLNL, spikes ~x100- x1000)

25. Central Part Prototype Vacuum Test
Small spikes (x1.5 – x 2) were obsreved
March/28 – May/09
225 rpm 9 x2
April 10th 7
Pressure [Pa] x10-6
Note: Linear scale
x1.5 5
4x10-6 Pa
3x10-6 Pa 3 1
28/Mar /Apr /Apr /Apr /May /May
Date
225 rpm

26. Central Part Prototype Vacuum Test Close-up of the small spikes
225 rpm
2 hours
3.5x10-6 Pa
x1.5 1 3 5 7 9
Pressure [Pa] x10-6
Note: Linear scale
Apr/21, 7:46 – Apr/22, 03:46
225 rpm

27. Central Part Prototype Vacuum Test Facts and What happened (1)
• Ion pump　100 litter/sec.
• Rotation at 225 rpm (design value).
• We started the experiment on February 9th.
• Vacuum level went good monotonically.
• And reached ~ 3x10-6 Pa at the end of March.
• Vacuum level was stable at ~ 3x10-6 until April 10th.
• Then, we observed small spikes.
- High of a spike ~x1.5.
(cf. Undulator target at LLNL, spikes ~x100- x1000)
- The time constant was minutes.

28. Central Part Prototype Vacuum Test
Small spikes (x1.5 – x 2) were obsreved
March/28 – May/09
225 rpm 9 x2
April 10th 7
Pressure [Pa] x10-6
Note: Linear scale
x1.5 5
4x10-6 Pa
3x10-6 Pa 3 1
28/Mar /Apr /Apr /Apr /May /May
Date
225 rpm

29. Central Part Prototype Vacuum Test Facts and What happened (1)
• Ion pump　100 litter/sec.
• Rotation at 225 rpm (design value).
• We started the experiment on February 9th.
• Vacuum level went good monotonically.
• And reached ~ 3x10-6 Pa at the end of March.
• Vacuum level was stable at ~ 3x10-6 until April 10th.
• Then, we observed small spikes.
- High of a spike ~x1.5.
(cf. Undulator target at LLNL, spikes ~x100- x1000)
- The time constant was minutes.
• Vacuum went gradually bad, it was ~4x10-6 on May 10th.
• Something seemed to be aging. Ferrofluid?

30. Central Part Prototype Vacuum Test
Conclusion (1)
• 3-5x10-6 Pa is kept with 225 rpm rotation with 100 l/s
ion pump.
• The vacuum level is the same as expected.
• It is promising.
• However we have concern for lifetime of the system.

31. Central Part Prototype Vacuum Test Facts and What happened (2)
• Something seemed to be aging. Ferrofluid?
• When ferrofluid aged, small air void penetrate via ferrofluid?
• We stopped rotation on May 11th

32. Central Part Prototype Vacuum Test On May/11, we stopped rotation
May/11 – May/15
x10 9 7 x3
Pressure [Pa] x10-6
Note: Linear scale 5
4x10-6 Pa 3
2x10-6 Pa 1
225 rpm
0 rpm
May/11 10:15, Stop Rotation

33. Central Part Prototype Vacuum Test Facts and What happened (2)
• Something seemed to be aging. Ferrofluid?
• When ferrofluid aged, small air void penetrate via ferrofluid?
• We stopped rotation on May 11th
- Vacuum level got better 4x x10-6.
- We observed larger spikes. The height was x3 – x10.
- Sikes were rather periodic. T = 5 hours 50 minutes.

34. Central Part Prototype Vacuum Test
May/ :22
0 rpm 9
15 seconds 7
Pressure [Pa] x10-6
Note: Linear scale 5 3 1

35. Central Part Prototype Vacuum Test Facts and What happened (2)
• Something seemed to be aging. Ferrofluid?
• When ferrofluid aged, small air void penetrate via ferrofluid?
• We stopped rotation on May 11th
- Vacuum level got better 4x x10-6.
- We observed larger spikes. The height was x3 – x10.
- Sikes were rather periodic. T = 5 hours 50 minutes.
- Sikes were very short term.

36. Central Part Prototype Vacuum Test Facts and What happened (2)
• Something seemed to be aging. Ferrofluid?
• When ferrofluid aged, small air void penetrate via ferrofluid?
• We stopped rotation on May 11th
- Vacuum level got better 4x x10-6.
- We observed larger spikes. The height was x3 – x10.
- Sikes were rather periodic. T = 5 hours 50 minutes.
- Sikes were very short term.
Conclusion (2)
• We don't quit understand the phenomena yet.
But, since situation changed when we stopped rotation,
we judged the aging of ferrofluid caused the deterioration
of the vacuum quality.

37. Central Part Prototype Vacuum Test
Next steps (1)
Our guesses
• We suspected aging of the ferrofluid caused the
deterioration of the vacuum quality.
• We suspected temperature rise of the ferrofluid by rotation
may affect the aging.

38. Central Part Prototype Vacuum Test
Next steps (1)
Our guesses
• We suspected aging of the ferrofluid caused the
deterioration of the vacuum quality.
• We suspected temperature rise of the ferrofluid by rotation
may affect the aging.
Next steps (1)
• We are going to enhance the cooling water channel.
• We added temperature monitor (thermocouple) at near
the ferrofluid seal (unfortunately not really near).

39. Central Part Prototype Vacuum Test
Enhancement of the Water Cooling Channel
Before Enhancement
OUT IN

40. Central Part Prototype Vacuum Test
Enhancement of the Water Cooling Channel
Before Enhancement
OUT IN
Rotating Water Seal
and
Inside the Shaft
are cooled

41. Central Part Prototype Vacuum Test
Enhancement of the Water Cooling Channel
After Enhancement IN
OUT IN
OUT IN
OUT

42. Central Part Prototype Vacuum Test
Enhancement of the Water Cooling Channel
After Enhancement IN
OUT IN
OUT IN
OUT
Rotating Water Seal,
Inside the Shaft,
Motor,
and Near Ferrofuild Seal
are cooled

43. Central Part Prototype Vacuum Test
Enhancement of the Water Cooling Channel
After Enhancement

44. Central Part Prototype Vacuum Test
We added thermocouple at near the ferrofluid seal

45. Central Part Prototype Vacuum Test
Next steps (1)
Our guesses
• We suspected aging of the ferrofluid caused the
deterioration of the vacuum quality.
• We suspected temperature rise of the ferrofluid by rotation
may affect the aging.
Next steps (1)
• We are going to enhance the cooling water channel.
• We added temperature monitor (thermocouple) at near
the ferrofluid seal (unfortunately not really near).
• We are going to change water temperature.
25 C (now) C C. We will do it begging of July.
• We will check lower limit of the temperature which doesn't
make condensation of the water in air.

46. Central Part Prototype Vacuum Test
Next steps (2)
Next steps (2)
• We will break vacuum on July 19th.
• The vacuum seal will be send back to Rigaku.
Rigaku exchange ferrofluid.
• We will reinstall the vacuum seal end of July.
• Then we will restart vacuum test with:
- fresh ferrofluid,
- enhanced cooling water channel,
- lower water temperature,
- and, improved temperature monitor.

47. Summary

48. Summary (1) Heat, Cooling, Stress Radiation trelance
• Detailed simulation study of heat, cooling, stress,
was done. OK (OK even for 2600 bunches)
Radiation trelance
• The radiation test of the ferrofluid was already done.
The ferrofluid is vital against 3-year ILC operation.
• The irraidation test of the whole system (motor,
bearing,,,) was done. No problem was found.
Central Part Prototype Vacuum Test (1)
• Long term test is ongoing (from Feb. 9th).
• 3-5x10-6 Pa is kept with 225 rpm rotation with 100 l/s
ion pump.

49. Summary (2) Central Part Prototype Vacuum Test (2)
• The vacuum level is the same as expected.
• It is promising.
• However we have concern for lifetime of the system.
Gradual deterioration of vacuum quality was observed
after two month of the operation.
• We suspected aging of the ferrofluid.
• We are going to make improvement and will
restart vacuum test with:
- fresh ferrofluid,
- enhanced cooling water channel,
- lower water temperature,
- and, improved temperature monitor.