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PSB C04 RF system Consolidation or upgrade? M. Paoluzzi – CERN BE-RF. C02 : 4 cavities in 2 straight sections freq= 0.6-1.8 MHz Vgap=8 kV Rs≈350 Ω seen by the beam C04 : 4 cavities in 1 straight section freq 1.2 3.6 MHz Vgap=8 kV Rs≈350 Ω seen by the beam

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Presentation Transcript
slide1

PSB C04 RF system

Consolidation or upgrade?

M. Paoluzzi – CERN BE-RF

slide2

C02 : 4 cavities in 2 straight sections

freq= 0.6-1.8 MHz

Vgap=8 kV

Rs≈350Ωseen by the beam

C04 : 4 cavities in 1 straight section

freq 1.2 3.6 MHz

Vgap=8 kV

Rs≈350Ωseen by the beam

C16 : 4 cavities in 1 straight section

freq 6.0- 16 MHz

Vgap=6 kV

Rs≈2 kΩ seen by the beam

slide3

Consolidation foreseen C02, C16

  • Replacement of ITL, power supplies, cables
  • (rebuilt the systems keeping the cavities and amplifiers)
  • Possibly move AVC and Tuning loops to Low Level
  • Consolidation foreseen C04
  • Same as above but power stage replacement
  • (improve mean available power and current for beam
  • loading compensation)
  • Is it the time to envisage a technology change?
slide4

Narrow band

Tuned systems

Highly optimized

Almost no room for Vgap increase

Further reduction of Rs very difficult

slide5

Finemet LEIR Cavity

  • A single cavity covers the range 0.35÷5 MHz
  • Cavity length 0.5 m
  • Gap voltage 4 kV (tested at 5 kV)
  • No tuning
  • AVC integrated in Low Level
  • But…
  • … diameter incompatible with PSB overlapped rings
slide6

Finemet in PSB

  • Maximum outer diameter OD=330mm
  • Inner diameter ID=200mm
  • Standard Finemet thickness 25mm
  • Two kind of material:
  • Standard LEIR like : FT3M (data available from small rings)
  • New low loss : FT3L (Thanks to KEK and Chihiro Ohmori for
  • providing data)
slide7

Air cooling test on small rings (OD=133mm) :

  • Simple blower on each ring side
  • With 500kW/m3 t MAX≈70°C
  • Maximum inside temperature unknown
  • Limit temperature
    • Suggested from Hitachi t MAX≤100°C
    • KEK booster experience t MAX≈100°C
    • J-PARC experience t MAX≈200°C for few hours
slide8

Minimum peak voltage

380V for FT3L

300V for FT3M

@ 1 MHz

Note:

f Injection ≈1 MHz with LINAC4

One C04

cavity contains 50 rings

In the range 1÷4 MHz :

VGAP=15÷17 kV with FT3M

VGAP=19÷29 kV with FT3L

slide9

Basically working

on a capacitor

Almost no difference with increased number of rings

slide10

Alternative approach based: use two rings (FT3L) and 1 gap

Each ring can accept 500pF and still cover the 1÷4 MHz band .

RPmin is ≈100 Ω (per ring)

P≈1500W for 700V across two rings

This can be supplied by a solid-state amplifier

(in PSB solid state amps used since 1987!!!)

beam current

Sine shape approximation

Beam current

φL , TL

For a pure h1 or h2 beam,

the beam peak current is 22.7 A @ ej

1st rf harmonic : ÎH1 = 9.56 A

2nd rf harmonic: ÎH2 = 6.06 A

w/o acceleration, the h1 bunch length:

φL 138o (2.4 rad or 220 nsh1 @ej.)

Total charges per bunch= 2 E13h1

(sinus shape approx.)

Slide provided by A. Blas CERN BE-RF

slide12

MRF157 Mosfet

600W up to 80MHz

To provide 800W

(2 units push-pull)

ID-peak≈32A

ID-DC≈10A

MRF151 Mosfet

150W to 175MHz

To provide 200W

(2 units push-pull)

ID-peak≈12A

ID-DC≈4A

slide13

Shunt resistance of each gap Rs≈200 Ω

  • To get the present 8kV need 12 gaps
  • Total impedance seen by the beam Rstot≈2400 Ω
  • Impedance of present cavities (including FB) ≈350 Ω
  • We must reduce Rstot and compensate beam loading with:
      • ≈20 dB RF feedback seems possible with 10 ns delay in the loop.
    • 1 turn feedback: difficult (nevertheless possible) because revolution time is only ≈500 ns at extraction.
    • Combination of both
slide14

The cavity could be used as combiner for push-pull operation and driven by 2 amplifiers similar to the LEIR 1kW drivers.

The total power could easily be

brought to 2 x 2 kW simply

increasing the DC supply by 15%.

The 120W (200W) power module

delay is 12 ns and the 9 ways

combiner 4ns. Both could be

reduced and 10 ns total seems

within reach.

slide15

Simulated system response:

1 Finemet ring driven by 9 combined 200W modules

and feedback including delay .

200W module.

1 ring impedance.

Amplification chain response.

slide16

Advantages

  • Modular system.
  • Reduced machine space and/or increased installed voltage.
  • Possibility of installing spare cavities as hot back-up.
  • No tuning loop.
  • Simplified solid-state system.
  • Risks
  • Additional new system at restart with LINAC4.
  • New technology and configuration.
  • Complete new design.
slide17

How could we proceed…

  • 2010-2011 Design and produce a first section.
  • … if successful then:
  • 2012 produce and install and test a full set of cavities for the required 8 kV.
    • They should fit in the place of one of the present C04 cavities.
  • 2013 Tests with beam (1 ring and C02 system still in place)
  • … if successful then:
  • 2014-2015 Proceed with full scale construction and
    • C02/C16 renovation
  • 2016 Installation
  • … but for security
  • 2011 Design a first C04 improved RF power amplifier.
  • 2012 Produce and install C04 improved RF power amplifier.
  • 2013 Tests with beam (1 ring)
  • 2014-2015 Depending on 2013 tests start C02/C04/C16 renovation or
    • stop C04 renovation it and proceed with new system.
  • 2016 Installation
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