wp4 summary · • wp4 part of pbs ok. cost estimate data ok. funded by the european union wp...

Funded by theEuropean Union

WP leaders meeting, CERN 3 and 4 December 2019 W. Wuensch, CERN

WP4 Summary

General observations:

• RF system and module baseline established. Overall parameters fixed and consistent with other WPs, going forward with detailed design.

• Long-range transverse wakes are being calculated for double bunch operation.• Harmonic linearizer 3 MW source baseline established. Full rf system including pulse

compressor established.• Work started on industrialization of accelerating structures.• WP4 part of PBS OK. Cost estimate data OK.



WP4 Summary

WP4.1 status

Linac RF design and optimization

Optimized X-band RF accelerating section designed on the base of specificationsprovided by other WPs, namely the average accelerating gradient (65 MV/m, WP2) andthe minimal average iris aperture of the cells (3.5 mm, WP6). State-of-the-art pulsecompressors have been included in the optimization.

Accelerating section design

The baseline accelerating section is TW type, 2π/3 phaseadvance, 90 cm long (108 cells) and shows a linearly taperediris aperture profile. A fine tuning of the entire structure toachieve the required field flatness is undergoing.

Complete model geometry and computed field distributionhave been transferred to WP6 for general beam dynamicsstudies and specific evaluations on BBU instabilities.



WP4 Summary

A baseline RF accelerating module has been defined for the Eupraxia@SparcLab project, consisting in 4structures powered by 1 RF klystron through a pulse compressor. This could be taken as a good reference forthe XLS module since the basic RF specifications are the same.

Two slightly different modules have been designed for the low-energy and high-energy linac sectors.

The module design has been based on a 50 MW, 1.5 µs, 100 Hz rep rate klystron (CPI VKX-8311A) capable todrive the 4 sections to the 65 MV/m nominal average gradient including a reasonable safety margin.

RF Accelerating module

WP4.1 status (cont’d)



WP4 Summary

Different scenarios have been considered to increase the operational rep rates towards the 1 kHz frontier at expense of a gradientreduction.

A first approach is based on the reduction of the RF pulse duration to the minimum allowed by the structure filling time (≈150 ns).250 Hz could be in principle reached but pulse compressors can not be used in this case.

A second approach is based on adding an additional RF power source to the module for high rep rate operation, which gives theoption of reaching 1 kHz at gradients larger than 30 MV/m.

Different linac configurations based on these modules are under considerations in collaboration with WP2.

High rep rate scenariosWP4.1 status (cont’d)

Funded by the

European Union

WP4, 1st August 2019 M. Aicheler, UH/HIP 3

Acc-Structure

Quad

103cm 12cm

Acc-Structure

Acc-Structure

Sector valve

10cm 5cm

Conn.

Baseline Module layout Low-Energy (up to 2 GeV)

Acc-Structure

Quad

Quad

Quad

Splitter

PC

Klystron/Modulator

Mode converters+ circular WG

100Hz@50MW1kHz@6MWPower

SwitchKlystron/Modulator

Module length: 5.10 m; RF-fill factor: 71%

Quad contains BPM&Corrector

Two WFM per AS with pumping

Funded by the

European Union


Acc-Structure

Quad

103cm 12cm

Acc-Structure

Acc-Structure

Sector valve

10cm 5cm

Conn

103cm

Baseline Module layout Medium-Energy (up to 5.5 GeV)

Acc-Structure

Quad

Splitter

PC

Klystron/Modulator





5cm



Funded by the

European Union


Acc-Structure

103cm 12cm

Acc-Structure

Acc-Structure

Sector valve

10cm 5cm

Conn

103cm

Baseline Module layout High-Energy (up to 5.5 GeV)

Acc-Structure

Quad

Splitter

PC

Klystron/Modulator









WP4 Summary

Task 4.3 Klystron and Modulator technologyInvestigating hardware choices for the three options of XLS linac and RF units Maintaining close contact with manufacturers to push for development of high rep rate tubes



WP4 Summary

List of existing and upcoming klystrons

CPI CanonExisting Prototype Existing Prototype Prototype

RF frequency [GHz] 11.9942 11.9942 11.9942 11.9942 11.424

Peak (RF) power output 50 6 6 8.2 20

Beam voltage [kV] 410 155 155 154 265

Beam (cathode) current [A] 310 97.6 95 94 170

Pulse repetition rate [Hz] 50 (100) 400 (1000) 400 (1000) 400 (1000) 400

Pulse width RF [us] 1.5 5.0 5.0 5.0 1.5

Efficiency [%] 40 43 44 56 44

ABP

Ou

tpu

t P

ow

er

(MW

)

Fourier Transform

of output shows

single peak at

36GHz

Over 3MW output power

Time (ns)

Simulated by

PIC-code

MAGIC 2D

Electron Phasespace (z,r)

z (mm)

r (m

m)

Frequency (GHz)

36GHz Gyro-klystron PIC simulations

EΦ field pattern in 3rd cavity

z (mm)

ABP

36GHz Gyro-klystron Verification

Input Mode TE01

Output Mode TE02

Verified by 3D PIC-code CST-PS

Input

Cavity

Output

Cavity

Collector

Intermediate

Cavity

ABP

36GHz Frequency, Input & Output Power

Frequency (GHz)

Voltage (kV) 150 Current (A) 50

Velocity ratio 1.4 Drive power (W) 400

Beam guide radius (mm) 2.3 Magnetic field (T) 1.46

36GHz Gyro-Klystron can operate a PRF of 1kHz

Power (MW) 3.0 Bandwidth 0.3%

Efficiency 40% Gain (dB) 39 (max 42)

2nd iteration cad files

Are the circular groves on one side

intended for brazing material?

What is the purpose of the linear

grove?

How is the disc alignment foreseen?

Disk diameter is now 60, could that be

80? (similar to CLiC)

■ Use the extra 10 mm for alignment

feature (like PSI style stepped ring)?

Nice parametric design!

good communication

Yes

Leak test

To be studied, external prism for

alignment, PSI type, ideas are welcome

and prototypes have to be done.

Yes

■ Yes

Questions VDL Answers

VDL proposal redesign for alignment

Assumptions

■ Extra 10 mm outside

Compatible with tooling for CLiC

Used to create rim for alignment

Rotational alignment feature to be

added.

Thermal design

Questions:

■ RF Power dissipated in structure?

E.g. Smart*Light = 2 kW

■ Macroscopic: power dissipation along structure?

E.g. S*L: 50% of 2 kW will be dissipated equally throughout the first 24 cells. The dissipation will then

decay to the last cell where 23 % (given a total length of 50 cells) will exit the structure and be input into the

load.

■ Microscopic: exact power distribution on cavity wall e.g. dominant on iris?

■ Design temperature and maximum allowed dT?

■ Maximum allowed water flow speed [m/s], laminar/turbulent?

1st simulations

Assumptions:

■ 4 l/min cooling with 30 degrees water per channel

■ 2000 W/m2 heat flux on purple surface in picture below

■ Convection/radiation on outer surface to 22 degrees

■ Isolated (no heat transfer) on both sides

Simulation in time

22 oC RT

30 oC

30.1 oC

t = 0 t = 300s t = 600s

30oC water on RF power on

Representative sketch, real simulation result will be added.

Results with power off and power on Cooling always on

Delta T over cell < 0.01 degree Celsius Delta T over cell = 0.1 degree Celsius t

t = 300 sec t = 600 sec

Delta T over cell < 0.01 degree Celsius Delta T over cell = 0.1 degree Celsius t

t = 300 sec t = 600 sec

Results with power off and power on Cooling always on

Outlook

Further detailing thermal model input needed

Further detailing alignment strategy

Setting up cost calculation / estimation based on latest models incl. alignment

Design rule:

CAD design with symmetrical tolerances to be compatible with state of the art CNC machine programming



WP4 SummaryThank you!

CompactLight is funded by the European Union’s Horizon2020 research and innovation programme under Grant Agreement No. 777431.

[email protected] www.CompactLight.eu

wp4 summary · • wp4 part of pbs ok. cost estimate data ok. funded by the european union wp...

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