1. ILC Accelerator Update
Recent design changes
Cost reduction
Mike Harrison

2. Design Changes - Beam dumps
Modifications due to adopting a more rational scenario for commissioning
and tune-up

3. ILC Baseline Tune-up Dumps
Design Changes - Dumps
ILC Baseline Tune-up Dumps
ILC Tune-up (abort) dumps with maximum design ratings
E+/E- Dumps 1,2,3 are at a fixed 5 GeV, with E+/- 6 at 15 GeV.
4,5 & 7 at 250 GeV or full energy.
All dumps except the main final E+/- 5 could have lower ratings with a reduced set of maximum beam parameters used during tuning.
Ewan P

4. Design Changes - cryogenics
Overview of request
The change request modifies the cryogenic plant layout from that proposed in the TDR. The main helium compressors and associated cryogenic storage tanks are moved from the underground cavern to the surface. An additional helium recovery compressor and backup power generator (1MW) is also added to recover the helium boil off from the cryomodules during a power outage or scheduled accelerator warm-up. A helium recovery line replaces a cryogenic transfer line. The proposed changes are shown schematically in figures 1 & 2. It is evident that the surface footprint is significantly larger and the tunnel cavern correspondingly smaller with these CR’s than the baseline design as described in the TDR.

5. Design Changes - cryogenics

6. Design Changes - cryogenics
Review Panel comments
The logistics of operations with the compressors on the surface are certainly improved (power, cooling, vibration, tunnel noise, maintenance, repair) the Panel find the most compelling reason for moving the compressors and liquid inventory is that of underground helium storage. Safety considerations of such a helium volume would impact many aspects of operation and make relatively routine operations such as maintenance essentially impractical.
Protecting the helium inventory during warm-ups, both planned and accidental, would also appear to be a crucial aspect of the system requirements which was not addressed in the TDR baseline. These CR’s rectify that omission.

7. Cost reduction - TDR Value Estimate 500 GeV (materials only)
By accelerator system
7.8 BILCU
ILCU = $FY12
Value estimate – no contingency, inflation, pre-ops, R&D, spares, etc….
Host
Note: ML only 55% of the CFS cost.
This breakdown based on DKS (mountainous).
Host
Host
By technical
system

8. Cost reduction How much could you save ?
The highest leverage cost element is in the accelerating gradient. To lowest order a gradient/Q increase would result in less cryomodules, less HLRF units, shorter tunnel, less cryogenics. A 10% increase in operating gradient -> 6-8 % decrease in total cost (see Kubo-san later today for SRF prospects)
Other items arising from ML value engineering ~ 2-5% ??? Most cost reducing activities that come under the general rubric of value engineering are relatively benign from a design perspective: tuners, couplers, HLRF, niobium stock, cavity & cryomodule process & production, etc… Thus most beneficial changes can be incorporated at any time within reason.
What else could we contemplate for cost reduction ?

9. Cost Reduction – Design Scope
De-scope the machine performance to lower cost.
Low energy operation. Reduce luminosity in the CoM energy regime in which the ILC was not designed for (< 300 Gev CoM) i.e. the Higgs mass). This will eliminate 10 Hz operation.
Change the specifications to remove the polarised positron requirement. This has a significant effect in many areas of the design. A non-polarised positron source is not straightforward either due to the high ILC positron flux but it remains significantly easier. A small added benefit would include the fact that we do indeed have a technical solution.

10. Cost Reduction – Design Scope
Smaller ML tunnel. Change requirements on personnel access – reduce shield wall -> smaller tunnel

11. Cost reduction - Machine Geometry
We could adopt the minimum (most risky) geometric solution. No cryomodule redundancy, no additional tunnel, “aggressive” accelerating gradient

12. Cost reduction – damping ring tunnel size
The damping ring tunnel in the TDR was sized to accommodate 2 positron rings in case electron cloud effects limited the positron intensity in a single ring. Subsequent studies indicated that this was unlikely.

13. Cost reduction – What could be hoped for
Assume the time scale is 2-3 years, and if everything worked out optimally then:
cavity with N-doping, gradient increase + ~10%

14. “standard” 120C bake vs “N infused” 120C bake
SRF R&D and Cost Reduction
“standard” 120C bake vs “N infused” 120C bake
Same cavity, sequentially processed, no EP in between
Achieved: MV/m  194 mT With Q ~ 2e10!
Q at ~ 35 MV/m ~ 2.3e10
Grassellino, Aderhold
Increase in Q factor of two, increase in gradient ~15%

15. Cost Reduction – Cavity processing
Potential process simplification
25%(?) reduction including some second pass fraction
sub-mm surface defects
equator weld (critical)
<20 MV/m
2nd Pass
Field emission
Thermal breakdown (quench)
< 35MV/m
A. Yamamoto

16. ILC assumed a ~10% degradation
XFEL Cryomodule performance
ILC assumed a ~10% degradation

17. Cost reduction – What could be hoped for
cavity with N-doping, gradient increase + ~10%
cavity process efficiencies/yield ~4% cost reduction
no cryomodule degradation, gradient increase + ~10%
SRF savings ~ 14%
design savings ~ 2-4% (200/400 MILCU)
value engineering ~ 2-4%
Maximum achievable cost reduction < 20% ???
Will need an aggressive R&D program and a discussion on acceptable performance risk to head in this direction.