The ISIS Dual Harmonic Upgrade The Council for the Central Laboratory of the Research Councils Andy Seville Joint Accelerator WorkshopMarch 28th, 2006

Add 2 nd Harmonic RF Component RF Phase → Dual Harmonic P Error → RF Phase → Single Harmonic Voltage → Enlarge Stable Region Optimise trapping Reduce Loss ISIS Dual Harmonic Acceleration 50% More Protons!

ISIS Dual Harmonic Acceleration The required Accelerating Field is given by V = Vo (sin  - .sin (2  +  ) ) The voltage on Cavity Gaps is V = -Vo sin (  ) + .Vo sin (2  +  ) where Vo and  are +ve.  and  chosen to minimise loss during injection, trapping and acceleration cycle

ISIS RF Systems - Overview 13kV pk at 12 1RF accelerating gaps +10kVpk at 8 2RF accelerating gaps

ISIS Dual Harmonic Acceleration Changing Bias Current changes inductance of ferrite & therefore resonant frequency of the cavity. Every 20ms:- InjectionExtraction Proton Energy70MeV800MeV Rotation Freq0.65 MHz1.55MHz 1RF Freq1.3 MHz3.1 MHz 2RF Freq2.6 MHz6.3 MHz Bias current200 A2000 A

2RF System Schematic LPRF Controls: Amplitude, Phase & Cavity Tuning Driver Amplifier Anode Power Supply 2 nd Harmonic high power RF Frequency Law Summing Amplifier Frequency Law Generator Master Oscillator 1.3 MHz MHz Dipole Search Coil Beam Phase Loop Radial Loop Trim Function Bunch Length Loop Existing Fundamental RF System  Phase Shifter Super- period Phase Splitter To Other 2 nd Harmonic Cavity LPRF Systems Phase Modulator 2 RF Level Controller Func Gen. 2 nd Harmonic Cavity Voltage Loop Func. Gen Phase Detector (Cavity Lock) Cavity Lock LPF 2 RF Detector RF Limiters Phase Detector (Cavity Tune) 2 Gated Summing Amplifier Delay Unit RF Summing Amplifier Phase Networks 2 2 nd Harmonic Cavity Phase Loop 2 nd Harmonic Cavity Tuning Loop Digital Signal Processor 2 nd Harmonic Beam Compensation Loop Sum Electrode Func. Gen. Func. Gen. LPF Variable Delay Variable Gain Frequency Doubler 2.6 MHz – 6.2 MHz 2 nd Harmonic low power RF HPD Cavity Cavity Bias Regulator Low Voltage Power Supply Cavity Lock Servo Cavity Gap A Voltage Monitor Summing Amplifier Phase Modulation and Delay Chassis 1RF 2RF A single Burle 4648VI tetrode is used to drive the 2RF cavity Phase Loop ALC Loop Beam Compensation Loop Cavity Tuning Loop

PSU - Splat! + PSU Tripping + ISIS Schedule + Machine Downtime

2RF Commissioning - Preliminary Results DHRF Acceleration beam intensity and beam loss (2 x 2RF Cavities) 93.5% 95%

Schematic of fundamental frequency and 2nd harmonic RF lock loop Var. 90  M. O. Phase Mod  az ±0  / 90  (  = 0  /-18  /- 36  ) Cavity Lock Phase Mod  Trim 1 RF. Cav.  Ref. 90  Cavity lock Phase Mod  Trim  Ref. Var.  Phase Mod Frequency Doubler Fundamental System 2RF System A B  az±45 Phase Mod  Det. 2 RF. Cav. Simulated by Cable Delay and Summing Amp

ISIS 2RF System Phase Modulation  2RF42RF52RF62RF8 Az Shift RF Phase RF Phase Phase offset for location of each system around ring

0° 2RF4 -90° +90° 2RF5 8:1 reduction in combined gap volts (simulated!) (SP4+SP5) / (SP4-SP5) ISIS 2RF System Phase Modulation 200V 10kV

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 0.2ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 0.3ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 0.4ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 0.5ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 0.6ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 0.7ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 0.8ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 0.9ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 1.0ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 1.5ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 2.0ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 3.0ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 4.0ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 5.0ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 6.0ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 7.0ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 8.0ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 9.0ms N - protons

Dual Harmonic Pulses Animated Version? DHRF Acceleration with 3 x 2RF cavities Beam 9.5ms N - protons

Theta Phasing Results 2RF SP5 APS Current SP4, 5 & 6 accelerating Theta = 0 Theta APS Current (with beam) 5Apk APS Current (no beam) 7Apk 0°0° -72° 2RF SP5 APS Current SP4,5 & 6 accelerating Theta

Challenges Solve Anode PSU tripping problem Complete cavity phasing tests DHRF Acceleration with all 4 2RF cavities Run 2RF Cavities reliably Increase beam current!