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Beam Monitors

Beam Monitors. Info from John Musson on new cavity receivers Other monitor issues. Cavity BPM performance*. Simulation: Cavity*receiver output = 4160  m* A (at 75 kHz bandpass, sampling output rate = 150 kHz) At low currents (50 nA):

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Beam Monitors

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  1. Beam Monitors • Info from John Musson on new cavity receivers • Other monitor issues

  2. Cavity BPM performance* • Simulation: • Cavity*receiver output = 4160 m*A • (at 75 kHz bandpass, sampling output rate = 150 kHz) • At low currents (50 nA): • 83mm at 150kHz. If we averaged over 0.5 seconds, we’d have a processor gain of ~270, and resolution of 0.3 mm. • This “averaging” can be done with firmware change to board [Alternative: We could modify our counting DAQ readout to average over some time window] • 20 dB LNA boosts signal 10x so 8mm at 150 kHz. Simple (connectorized) addition. • CONCLUSION: Musson is very confident this can be done *As rated by electronics group

  3. Cavity BPM performance* • Simulation: • Cavity*receiver output = 4160 m*A • (at 75 kHz bandpass, sampling output rate = 150 kHz) • At high currents (50 A): • 83 m at 150kHz. When we average over 30 ms, we’d have a processor gain of ~70, and resolution of 1.2 m. • Non-ideal system may have less processor gain, but this can be tested in bench test to get a “first-principles” estimate of beam monitor resolution. Receiver boards, V1.2 (as used by G0) are available and ready for installation.We should communicate on final details (like offset levels) and push development of low-current mode to be completed before end of summer.

  4. Existing Cavity BCM • Two cavities, each read out by two parallel, analog down-convertors: • 1 MHz - Most stable and reliable system (but old)! • 10 kHz - chosen to match bandpass to other readout electronics, very sensitive to small drifts of reference oscillator New cavity BCMs use different electronics, readout in a different crate. Provides good opportunity to test for common-mode current monitor noise. *As rated by electronics group

  5. What kind of beam noise might there be? Frequency spectrum from FFT can be viewed for new cavities (75 kHz) or the beam loss accounting current monitors (~100kHz) Similar is available from stripline BPMs, but limited to lower frequencies (few kHz?)

  6. Other beam monitor issues • Second dispersive BPM: • presently no redundancy in energy monitor • Spot size upper bound? • Can we find a way to “dither” spot size (at source) to measure sensitivity? • Where will our upper bound on spot size come from?

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