Other Technologies / Energy Efficiency Session Weiren Chou eeFACT2016 Workshop October 24-27, 2016, Cockcroft Institute, Daresbury, England W. Chou eeFACT2016, Oct 24-27, 2016

NEG New klystron Beam dump New klystron New magnet New Beam dump W. Chou eeFACT2016, Oct 24-27, 2016

W. Chou eeFACT2016, Oct 24-27, 2016

CEPC Power Consumption (ref. Pre-CDR) Efficiency (AC to beam) = 20%

FCC-ee total power subsystem Z W ZH 𝒕 𝒕 LEP2 (av.2000*) TLEP𝒕 𝒕 * M. Ross TLEP𝒕 𝒕 ** 2013 collider total RF power 163 145 42 217 185 collider cryogenics 2 5 23 39 18 41 34 collider magnets 3 10 50 16 14 booster RF + cryo 4 6 7 - booster magnets 1 injector complex <10 ? physics detectors (2) 9 cooling & ventilation*** 47 49 52 62 26 general services 36 20 total 275 288 308 364 120 359 284 for comparison, total CERN complex in 1998 used up to 237 MW *M. Ross, ``Wall-Plug (AC) Power Consumption of a Very High Energy e+/e- Storage Ring Collider,'‘ 3 August 2013, http://arxiv.org/pdf/1308.0735.pdf ; **M. Koratzinos et al., ``TLEP: A High-Performance Circular e+e- Collider to Study the Higgs Boson'', Proc. IPAC2013 Shanghai, 12--17 May 2013, {http://arxiv.org/pdf/1305.6498.pdf 2013, *** private discussions with M. Nonis presentation at IPAC’16 *dividing total energy used by 200 days 5

Power Consumption (2012 data) CERN: current average 183 MW (R. Saban) Fermilab: 2010 average 58 MW (D. Wolff)

Electricity Bill For a 500 MW collider in China: Fermilab: $ 440k per MW-year $ 20M a year (5 US cents per kWh) CERN: 1,200 GWh /year CHF 65M a year (5 Swiss cents per kWh) For a 500 MW collider in China: Assuming 1.5 “Snowmass unit” a year for operation: 500 MW x 4000 hours = 2 x 109 kW-hr Electricity price in China: RMB 0.5 yuan per kW-hr Yearly cost: RMB 1B (US$ 150M) (50 Chinese cents per kWh)

CEPC Relative Power Consumption (Pre-CDR) 3% 2% 9% 10% 6% 16% 5% 48%

Constable W. Chou eeFACT2016, Oct 24-27, 2016

Constable W. Chou eeFACT2016, Oct 24-27, 2016

Constable W. Chou eeFACT2016, Oct 24-27, 2016

Constable W. Chou eeFACT2016, Oct 24-27, 2016

Constable W. Chou eeFACT2016, Oct 24-27, 2016

CPD method applied to Gyrotron Watanabe Collector To improve the efficiency of high-power source, the CPD (Collector Potential Depression) method already was developed to apply the Gyrotron. (Up to 10 ~ 20 %) http://www.toshiba-tetd.co.jp/eng/product/ prden.php?type=cat&search=400000200000 In this case, an ceramics insulator is used to insulate between the collector and the body to be applied high-voltage of Vc (~ 30 kV) for an energy recovery. The energy spread of spent beam at operation is important for it. At saturation, the spent beam has small energy spread through electromagnetic interaction in the cavity. Therefore, ~ 30 kV of Vc can apply on the gap to pick-up as the electrical power from the spent beam to the outside of gyrotron after generating rf power. Spent beam Insulator Vc Vc 0~30 kV Ref. PHYSICAL REVIEW LETTERS, Volume 74, Number 26, pp 3532-3535, 26 December 1994 K. Sakamoto et al., “Major Improvement of Gyrotron Efficiency with Beam Energy Recovery”

How to apply CPD method to klystron Watanabe *An insulator needs to insert between the body and the collector to isolate the collector from body. Schematic diagram of one for CPD Conventional Collector High-voltage applies to Collector-body Isolate a collector from body to apply high-voltage for energy recovery. Without insulator Ground Vc Insulator and gap クライストロン電源は既存の構成を出来るだけ保持する方式を考える。下図はVkとVcを直列にする「Power=(Vk+Vc)*Ib」が、 後述する並列「Power=Vk*(Ik+Ic)」または、6.6kV交流へ変換し既存電源の入力とする方式を考えている(詳細検討未だ)。 RF out Vk Vk Body is a ground.

Example of the Power balance of klystron within without CPD Watanabe Collector loss Without CPD -> 420 kW With CPD -> 184 kW (recovery: 236 kW ) UHF 508.9 MHz RF out: 300 kW (CW) RF in: ~ 2W (CW) Example of : Toshiba E37703, CPD In case of 300 kW RF output (η = 42%) power, * Without CPD (Vk = 90 kV、Ib = 8 A) 　Required DC power is 720 kW -> RF out 300 kW, Dissipate power in Collector 420 kW * With CPD (Vk = 90 kV、Ib = 8A、Vc = 30 kV) 　η = 42 -> 62% -> RF out 300 kW Dissipate power in Collector 184 kW 　Recovery power 236 kW <- Pick-up by cable from collector, then reuse to drive a klystron After driving CPD, the required DC power is shifted to about 500 kW using by recovery power from the collector. Power picks by cable 3Φ AC 6.6 kV, ~ 270 A 90 kV, 8 A -> 720kW supply KPS, DC power supply (90 kV, Max 20 A)

The proposed layout for the main dipoles features a twin aperture yoke and busbars to provide the Ampere-turns Zimmermann I = 3570 A, B = 50 mT 320 mm 90 mm 210 mm 120 mm 60×80 mm 450 mm 0.5 T 1.0 T

Also for the quadrupoles a twin design with a 50% power saving is possible, with an F/D polarity constraint Zimmermann NI = 13500 A (287 A × 47 turns) B’ = 8.71 T/m 320 mm 88 mm dia 520 mm 640 mm 0.75 T 1.5 T

The resistive power for the bending magnets at 175 GeV is about 15 MW Zimmermann at 175 GeV current density [A/mm2] total power, 2 apertures [MW] twin pure dipole 0.7 10.1 twin combined function 0.9 12.9 Al conductor losses in interconnects / cables to be considered, likely 20-30% depending on arc filling factor and location of power converter(s)

The resistive power for the quadrupoles is about of factor of two lower if the combined function lattice is used Zimmermann at 175 GeV current density [A/mm2] total power, 2 apertures [MW] (modified) pure dipole lattice 2.3 21.5 (modified) combined function lattice 2.0 12.4 (7.8 twins + 4.6 single) Cu conductor cable losses to be added, for quadrupoles likely only a few % if twins are not used, then the power goes up to 43 MW for the pure dipole lattice, and 20 MW for the combined function one

W. Chou eeFACT2016, Oct 24-27, 2016 Apyan

W. Chou eeFACT2016, Oct 24-27, 2016 Apyan

W. Chou eeFACT2016, Oct 24-27, 2016 Apyan

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Chao

Chao

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Comparison of PSD from 316LN and NEG Malyshev Comparison of PSD from 316LN and NEG Samples coated with Ti-Zr-V at CERN (Switzerland) Experiments on the SR beam line at BINP (Russia) Stainless Steel (baked at 300C for 24 hrs) V.V. Anashin et al, Vacuum 75 (2004) p. 155. TiZrV coated vacuum chambers (activated at 190C for 24 hrs)

NEG coating for accelerators Malyshev NEG coating for accelerators First used in the ESRF (France); (APS, USA?) ELETTRA (Italy); Diamond LS (UK); Soleil (France) – first fully NEG coated; LHC (Switzerland) – longest NEG coated vacuum chamber; SIS-18 (Germany); MAX-IV (Sweden); Solaris (Poland) and many others. Meanwhile: NEG film capacity for CO and CO2 is ~1 ML: If P = 10-9 mbar then 1 ML can be sorbed just in ~103 s; Lab measurements of different NEG coatings often don’t repeat CERN’s data on sticking probability and capacity; However, NEG coated parts of accelerators work well.

Malyshev SEY from NEG

Summary Huge power consumption of high energy circular e+e- colliders (CEPC, FCC-ee) is a potential bottleneck and must be addressed at the early stage of R&D because it will take a long time to get real useful solutions. The biggest power sucker is RF, followed by magnet. Two parallel efforts (HEIKA and KEK/Toshiba) to develop high efficiency klystrons are very important and should be encouraged and supported. New magnet design (CERN) for reducing power consumption also points to the right direction. Plasma beam dump (UC Irvine/KEK/SLAC) has the potential for energy recycling. NEG coating technology has made significant progresses in the past 30 years. W. Chou eeFACT2016, Oct 24-27, 2016