The 20 kW Upgrade

1
The 20 kW Upgrade

• D. Douglas

2
Overview

• What we have now
• Where we intend to go
• First thoughts on how to get there

3
IR Demo Performance/Lessons

• Successfully operated optical cavity-based low
  extraction efficiency, low peak/high ave. power
  IR FEL driven by low peak/ high ave. power energy
  recovering SRF linac
• 2 kW CW IR power
• variable wavelength on 3 - 6 mm

4

• High power SRF linac operation
• driver linac operated from 36 to 48 MeV
• currents from 0 to 5 mA CW
• Energy recovery
• use waste FEL drive beam to power linac at
  currents in excess of 1 mA
• essentially all linac RF from FEL drive beam
• management of large momentum spread beam
• energy compression/longitudinal matching
• large acceptance optics
• High brightness source
• long cathode lifetimes (many 100s of C)
• good beam quality

5
The Path to 20 kW

• Turn up the wick
• Increase output power by raising drive electron
  beam power (6x), FEL extraction efficiency (2x)
• Broaden bandwidth 2 - 20 mm

6
Parameter Comparison

• Demo daily Demo best 20 kW
• I 5 mA 10 mA
• (60 pC/75 MHz) (110 pC/37 MHz) (110 pC/37 MHz)
• E 36 - 48 MeV 20 MeV 100 - 200 MeV
• sl, sdp/p 400 fsec,0.25 200 fsec,0.5
• eN 10 mm-mrad 6 mm-mrad 30 mm-mrad
• h 1/2 gt1.5 1
• (Dp/p)max gt5 6-8 (?) 10
• higher beam power, higher extraction efficiency Þ
  higher IR output
• transverse phase space performance -
  irrelevant for IR, matters for UV follow-on

7
Machine Concept

• Upgraded injector
• 10 mA (75 MHz/135 pC) gun
• double available RF power
• 3 module 160 MeV energy recovering linac
• reuse present module, add a twin
• out-year 3rd module 7-cell Jlab upgrade design
• large acceptance recirculator with full phase
  space match into/out of FEL
• FEL
• NG electromagnetic wiggler
• 32 m high power (16 m low power?) optical cavity
  in backleg

8
Schematic

9
Technical challenges

• beam quality at high bunch charge
• beam dynamics
• CSR/BBU/other wakefield/space charge/...
• phase space management
• transport large momentum spread
• energy recovery over larger dynamic range
  (longer linac)
• litany of errors - magnets/powering, coupler
  fields, alignment
• making it fit
• getting much larger machine into vault
• interleaving upgrade construction (which will
  eventually decommission existing machine) with
  Demo operations

10

• UV follow-on issues
• still higher required beam quality!
• energy reach of linac
• 1 pass limited to maybe 170 MeV?
• accelerator system design (more making it fit)

11
Cost

12
Schedule