ILC prototype undulator project ILC positron source meeting 31 st Jan – 2 rd feb 2007 @IHEP...
-
Upload
george-egbert-french -
Category
Documents
-
view
216 -
download
4
Transcript of ILC prototype undulator project ILC positron source meeting 31 st Jan – 2 rd feb 2007 @IHEP...
ILC prototype undulator project
ILC positron source meeting 31stJan – 2rd feb 2007
@IHEP Beijing
James RochfordFor the
HeLiCal Collaboration
HeLiCal Collaboration
CCLRC Technology Rutherford Appleton Laboratory:D.E. Baynham, T.W. Bradshaw, A.J. Brummitt, F.S. Carr, Y.
Ivanyushenkov, A.J. Lintern, J.H. Rochford
CCLRC ASTeC Daresbury Laboratory and Cockcroft Institute:A. Birch, J.A. Clarke, O.B. Malyshev, D.J. Scott
University of Liverpool and Cockcroft Institute: I.R. Bailey, P. Cooke, J.B. Dainton, L.J. Jenner, L.I. Malysheva
University of Durham, CERN and Cockcroft Institute :G.A. Moortgat-Pick
DESY:D.P. Barber, P. Schmid
Talk outline
• Specification of an undulator for the ILC• 3d modelling of the undulator
– Defines period and bore for operating point 80%
• Why operate at 80% short sample • Benefits of operating at 90%• Latest test results from experimental prototypes• Summary
Undulator specification
• Undulator period: as close as possible to 10 mm• Field on axis: to produce 10 MeV photons (first
harmonic)• Field homogeneity: ≤1% • Vacuum bore: to have beam stay clear of 4 mm
=> about 5 mm for vacuum bore and about 6 mm for magnetic bore
• Superconductor (NbTi) working point : about 80% of short sample critical current.
• Modular design -module length: 4 m
Modelling-predictions
3d model of undulator with iron poles
High mesh density Iron
Conductor
Bore
To deliver 10MeV photons assuming 7 wire wide
1:1 NbTi winding with operating point of 80%
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
2.0 4.0 6.0 8.0
Bore(mm)
Pero
id (
mm
)
3d models (wire peak)
3d models (block peak)
2d models
Linear (3d models(wire peak))Linear (2d models)
Linear (3d models(block peak))
Conclusion for NbTi a period of 10 mm means very small bore -
unpractical!Realistic figures:
Beam stay clear – 4 mmVacuum bore - 5 mmWinding bore - 6 mmPeriod - 11.5 mm
Modelling predicts relationship between the bore and period
Why operate at 80% 1
The RAL design is based on operation the magnet at 80% along the magnet peak field load line
This choice is one of the factors which limits the minimum period that can be obtained for a given bore
A design based on operation at 90% could allow some reduction in period or an increase in the bore
The justification for operation at 80% is now given
The gains from operation at 90% are quantified
Factors defining operating point/margin
Variation in operating temperature•Local variations within the magnet
•Global due to operation from a refrigerator at higher To or higher pressure
Variation in Jc superconductor value ? 1-2% mabye as much as 5%
Variation in Cu:Sc
Figure typically quoted (+/-10%)
Why operate at 80% 2
Magnet quenching•Enthalpy margin
•simplest criterion – energy to raise winding from Top to Tc (critical temperature)
•Minimum propagating zone (MPZ) – minimum quench energy (MQE)
•Defines the size of normal (non-superconducting) zone which can exist without developing into a magnet quench
•Characteristic length L~((2k(Tc-To))/(Jc^2xrho))^0.5
•k=thermal conductivity,Tc= critical temp, To= Op temp,Jc= critical current density, rho =resistivity
•For the undulator typically – MPZ length ~ 10mm Energy to Quench ~ 50microjoules
•Reliable operation is the balance between energy releases in the winding (wire movement-resin cracks) and stability margin
•In the undulator the energy releases will probably be small ( stresses are small) – very difficult to estimate energy release spectrum
Why operate at 80% 3
Magnet Op points
0
200
400
600
800
1000
1200
1400
1600
0 0.5 1 1.5 2 2.5 3 3.5
Field Tesla
Win
din
g C
urr
en
t De
nsi
ty
Jc wind @Top
Jwind vs Bp
Jop
This is calculated for Prototype 4
operating at 80% at 4.2k
It equates to a temperature margin
of 1.2K i.e it equivalent to
operating at 100% at 5.4K
J cNbTi(5T,4.2) A/mm 2̂ 2824
Top K 5.4
Cu:Sc 1.35wire overall diameter mm 0.44Ic 5T 4.2K Amps 151.01Axis Field B(T) 0.79Bp operating field B(T) 2.3J w operating current density A/mm 2̂ 855Iop Amps 166J w/J c along load line(4.2K) % 80Temp margin K 1.2
Why operate at 80% 4
What does the operating point mean in terms of temperature margin?
% %Operating Point 80 90Operating Temperature K 4.2 4.2Critical temperature K 5.4 4.8Temperature margin K 1.2 0.6Enthalpy Margin relative 539 220Cu:Sc 0.9 0.9tolerance = -0/+0.1Cu:Sc max 1 1Operating Temperature K 4.2 4.2Critical temperature K 5.2 4.6Temperature margin K 1 0.4Enthalpy Margin relative 420 137
J c NbTiDesign(NbTi,5T,4.2K) A/mm 2̂ 2824 2824Actual - 5% 2542 2542Operating Temperature K 4.2 4.2Critical temperature K 5 4.3Temperature margin K 0.8 0.1Enthalpy Margin relative 314 31
Operating TemperatureOperating Temperature design K 4.2 4.2Operating Temperature Operation K 4.5 4.5Critical temperature K 5.4 4.8Temperature margin K 0.9 0.3Enthalpy Margin relative 440 121
Operating point
80% to 90% halves the enthalpy dt 1.2k- 0.6K
Why operate at 80% 5
Sensitivity analysis
Aim here is to quantify effect of parameter variation on temperature margin and enthalpy margin. Note the enthalpy margin is a relative value
Variation in Cu:SC
@80% dT reduced by 0.2K
@90% dT reduced by 0.2K
Variation in operating temp
@80% dT reduced by 0.3K@90% dT reduced by 0.3K
Variation in JC in NbTi@80% dT reduced by 0.4K@90% dT reduced by .5K
Benefit operating at 90% 1
Period Vs bore for diff erent operating points Assumed
J c=2850@5T,4.2K, f rom Vac
10.0
10.5
11.0
11.5
12.0
12.5
4.0 5.0 6.0 7.0 8.0Bore(mm)
Peri
od (
mm
)
7 wire 1:1 NbTi ribbon operating at 80% of SS
7 wire 1:1 NbTi ribbon operating at 90% of SS
Linear ( 7 wire 1:1 NbTi ribbon operating at80% of SS)Linear ( 7 wire 1:1 NbTi ribbon operating at90% of SS)
Gains
Reduction in magnet period estimated for operation at 90% of short sample rather than 80% ~ 0.25mm
Increase in bore ~ 0.5mm
Only one of these is available
Reduction in manufacturing cost is insignificant
Magnets should operate in a long string without quenching
Mass production in industry – variations in fabrication quality
Need allowances for
•variations in operating temperature (pressure)
•variations in wire properties Jc(NbTi) and Cu:Sc ratio
•for enthalpy margin/stability
All the effects have been quantified in previous slide
If these effects are assumed to be additive – which they can be – An operating point at 90%of short sample wire performance leaves magnet operation vulnerable to very small variations in fabrication and operating parameters.
Whilst the benefits of increasing the operating point to 90% are marginal
So we consider 80% to be the correct design choice for the undulator
Operating point – conclusion
Prototypes programme 1
Experimental programme at RAL:
•To verify modelling and prove technology
•Series of five prototypes
•Last one has just been tested
Final 500mm long
prototype-
Prototypes programme 1
Experimental programme at RAL:•To verify modelling and prove technology
I II III IV V
Former material Al Al Al Iron Iron
Pitch, mm 14 14 12 12 11.5
Groove shape rectangular trapezoidal trapezoidal trapezoidal rectangular
Winding bore, mm 6 6 6.35 6.35 6.35
Vac bore, mm 4 4 4 4.5
(St Steel tube)
5.23*
(Cu tube)
Winding 8-wire ribbon,
8 layers
9-wire ribbon,
8 layers
7-wire ribbon,
8 layers
7-wire ribbon,
8 layers
7-wire ribbon,
8 layers
Sc wire Cu:Sc 1.35:1 Cu:Sc 1.35:1 Cu:Sc 1.35:1 Cu:Sc 1.35:1 Cu:Sc 0.9:1
Status Completed and tested
Completed, tested and sectioned
Completed and tested
Completed and tested
Test is in progress
1st results from prototype V
Prototype V fi eld profi le
-1
-0.5
0
0.5
1
0 100 200 300 400 500
Z, mm
Fiel
d on
axi
s, T
Prototype V details
Period : 11.5 mmMagnetic bore: 6.35 mmConfiguration: Iron poles and yoke
Measured field at 200A (RAL PSU):
0.822 T +/- 0.7 %
Prototypes programme 2
Prototypes programme 3
Prototype V training
0
50
100
150
200
250
300
350
0 2 4 6 8 10 12
Magent runup
Que
nch
curr
ent (
A)
23/01/2007
25/01/2007
Prototype V:•Did not go straight to full field before
quenching•Magnet warmed
between 23-25th to ~150K before
testing recommenced
•Reason for training is not
known may be due to impregnation
problem
Quench current 316A
Equates to a field of 1.1T in bore
Prototypes programme 4
Prototype V:•Achieved a higher critical field than
that predicted from manufacturer
nominal values •The implication is
the wire we are using is at pretty good in terms of super conductor
content. •If we assume the
upper limit then the observed quench current agrees
exactly with the calculated value
0
50
100
150
200
250
300
350
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
Field (T)
Curr
ent
(A)
Bp modelled (T)
Bo modelled (T)
Jcrit measured (A)
American Scond' data: Type 56S-53 ,d=0.4, nom' cu:sc (0.9 +/-.1)
American Scond' data: Type 56S-53,d=0.4,max cu:sc 0.8
American Scond' data: Type 56S-53,d=0.4 ,min cu:sc 1
Field on axis vs. Undulator period
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
6 8 10 12 14 16 18
Period, mm
Fie
ld o
n a
xis,
T
K=1
10.7 MeV -photons
Achieved with Al-former(Prototype I)
Achieved with Al-former(Prototype III)
Achieved with iron former(Prototype IV)
Achieved with iron formerand iron yoke (Prototype IV)
Achieved with Prorotype V(iron former and iron yoke)
Field is measured at 200A
Prototypes programme 5
Conclusions
Experimental programme at RAL:
•Modelling of a undulator capable of satisfying the ILC requirements has been completed
•The chosen the technology is to use NbTi ribbon operating at 80% of short sample
•The testing of the series of five prototypes has been completed
•Work on the design and manufacture of a full scale 4m prototype is now the priority and is well
underway.