# Presentation: 663687

## 8 GeV Superconducting LinacWith X-Ray FEL and 8 GeV Spallation & Neutrino Source

- 8 GeV Superconducting LinacWith X-Ray FEL and 8 GeV Spallation & Neutrino Source

## Project Information

- 125 Page Design Study
- Cost Estimate Spread Sheet  w/ BoE
- Big Pile of Useful Papers
- 		sorted by category
- _http://tdserver1.fnal.gov/project/8GeVlinac_

## 8 GeV Superconducting LinacTECHNICAL SUBSYSTEM DESIGNS EXIST AND WORK

- SNS Cavites

- FNAL/TTF
- Modulators

- “TTF Style” Cryomodules

- Civil
- Const.
- Based on
- FMI

- RF
- Distribution*

## COST ESTIMATE (detail available online)

- $ 284 M  + 30% Tax   =  $ 369 M

## 8 GeV Linac Baseline   2 MW

## RF - Klystrons

- 402.5  MHz / 2.5 MW   (7 total)
-  805    MHz / 5.0 MW  (10 total)
- 1207.5 MHz / 10 MW  (36 total)
- Also the possibility of standardizing on TESLA frequencies and eliminating          805 MHz entirely

- SNS Actual

- TESLA Design
- Scaled by ~ 7% from 1.3GHz

## Slide 7

## RF Power Budget & Coupler Power

## RF Fan-out for 8 GeV LinacA. Moretti, D. Wildman

## RF Fanout at Each Cavity

## 805 MHz RF Distribution in Tunnel

- No Active Electronics in Tunnel
- – only Ferrite & Bias Coils.

## RF Distribution Technical Parameters

## Modulators for Klystrons

- Biggest single component in RF costs
- Pfeffer, Wolff, & Co. (FNAL BD) have been making TESLA spec modulators for years
- FNAL Bouncer design in service at TTF since 1994

## Modulator Circuit

- IGBT / Capacitor Discharge circuit
- Bouncer to maintain flat top
- Redundant Switch with Ignitron Crowbar
- Pulse Transformer 10kV to 130 kV (typ.)

*H. Pfeffer, D. Wolff, & sons.*

## Slide 15

## 8 GeV  Klystron Gallery Floor Plan

- Linear array of equipment - simpler than SNS
- Much more room allocated for electronics     than TESLA design

## TESLA Tunnel & Klystrons

## TESLA RF DISTRIBUTION SYSTEM

## “SNS March 2000” Design, 12 Cavities / KlystronIndividual + Collective Cavity Control

- SNS pursued & dropped due to lack of R&D time

## SNS Final Baseline RF Design 1 Klystron Per Cavity, Individual Control

- Conceptually simpler but ~10x more Klystrons

## Fast Ferrite Phase Shifter R&D

- Provides fast, flexible drive to individual cavites                of a proton linac,  when one is using a                                  TESLA-style RF fanout.  *(1 klystron feeds 12-36 cavities) *
- Also needed if Linac alternates between e and P.
- This R&D was started by SNS but dropped due to lack of time.  They went to one-klystron-per-cavity which cost them a lot of money (~$20M / GeV).
***Making this technology work is key to the financial feasibility of the 8 GeV Linac.***

## ELECTRONICALLY ADJUSTABLEE-H TUNER

- FERRITE LOADED SHORTED STUBS
- CHANGE ELECTRICAL LENGTH DEPENDING ON DC MAGNETIC BIAS.

***TWO COILS***  PROVIDE INDEPENDENT
***PHASE AND AMPLITUDE *** CONTROL OF CAVITIES

- Attractive Price Quote from AFT
- (<<  Klystron)

## Slide 23

## Slide 24

## Ferrite Phase Shifter High-Power Test Stand

- 805 MHz Klystron
- 12 MW x 100usec
*(need: 0.5 MW x 1 msec)*
- _First goal: _
-     See if existing YIG tuner functions at 500kW. ***(yes!)***
- _Ultimate Goal:_
- 0.2 dB loss for
- 360 deg. phase shift
- in 100~500usec.

- Door-knob
- Transition

- YIG Ferrite
- Phase Shifter

- Dry Load

- Ferrite
- Bias Supply

- Hybrid
- Tee

- 12 MW
- Klystron

***A. Moretti, D. Wildman***

## Tuners and Cavity Resonance Control

- TESLA R&D has shown that piezoelectric tuners can correct for Lorentz detuning and cavity microphonics in a 1 ms pulsed SC linac.
- SNS Cavity assemblies used for cost basis include *both* Mechanical and Piezoelectric tuners
- RF phase and amplitude control provided for individual cavities via fast ferrite phase shifters.
- Simulation (& SNS experience) needed to determine bandwidth requirement of shifters.

## Slide 27

## At What Energy and Klystron Fanout  does Vector Sum Regulation Work?

- If TESLA-style Vector-Sum Regulation works:
- No need for FAST phase shifters
- No need for Ferrite Phase Shifters at all if we start with H-/protons only.
- Design Study assumes Vector Sum works in Beta=1.00 section.
- Marcus Huening embarking on detailed simulation

## Slide 29

## RF Phasing in Linac for Protons vs. Electrons

- Cavity cell length changes as proton accelerates
- not all cavities can be same design
- lose some gradient by running off design 
- Protons are non-relativistic
- energy error  downstream phase error
- Protons run off-crest
- only get ~85% of accelerating gradient at crest
- more sensitive to phase errors
- Must change cavity phases to accelerate electrons and protons on alternate cycles

## Slide 31

## Summary of Phase Shifter Specs805 MHz and 1207.5 MHz

## Phase and Amplitude Tuner Specs

## Staging & Cost Reductions

- Preserve 2 MW beam power Main Injector
- Need 1.5E14 ~25uC per linac pulse.
- Reduce stand-alone power of 8 GeV Linac from 2 MW 0.5 MW
- Beam current: 26mA  8.7mA
- Beam Pulse Length: 1msec  3 msec
- Rep Rate: 10Hz  2.5 Hz
- Klystron Count: 41  ~12-17
- Option to install the rest as later 2 MW upgrade
- Investigate SCRF front end instead of DTL.

- Same
- Charge
- Per Pulse

## 8 GeV Linac Baseline   2 MW

## 0.5 MW with SNS Frequencies

## 0.5 MW with SCRF Front End

## 0.5 MW with TESLA Frequencies & SCRF F.E.

## SCRF Front End Option

- Replace DTL with independent, low-power SCRF resonators
- RF system ~1/5 the size (total watts)
- 300 MHz - 400 MHz
- Independent power tubes,
-    or Fan out power from one big tube to many resonators?

## Petr Ostroumov

***Petr Ostroumov***

## SNS 402.5 MHz

- Klystron

- Radial Combiner
- (or Fanout)