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Region 29 Quad 501 Test

This study characterizes the RMS noise of Linac quad power supplies within the 0.1 Hz to 10 Hz range. The goal is to ensure compliance with LCLS PRD specifications of less than 0.05% RMS stability over ten seconds. The aging 20+ year power supplies utilize SCR control via SLAC transductors. Current measurements were conducted using sophisticated setups, reading multiple points to analyze absolute and relative RMS noise. Results indicate the current supplies meet required stability thresholds; however, they exceed 100 times typical noise levels for modern systems. Data files are available for further analysis.

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Region 29 Quad 501 Test

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  1. Region 29 Quad 501 Test • Purpose: Characterize RMS noise on Linac Quads in the 0.1 Hz to 10 Hz region • LCLS PRD specifies less then 0.05% RMS stability over 10 seconds • Linac Quad power supplies are 20+ years old • Bulk supply is SCR controlled using a SLAC transductor for current regulation • Boost supply uses an internal shunt for current regulation • The RMS noise in the 0.1Hz to 10Hz region has never been measured

  2. Region 29 Quad Configuration • Each region has 8 Quad magnets connected in series • Each string has a 200 amp SCR bulk supply • Each magnet has a 20 amp boost supply • Need to measure the current in the bulk and boost power supplies simultaneously to determine actual magnet current

  3. Test Setup • Zero Flux transductors to read bulk and boost current • Two HP3458A meters to read the two transductors simultaneously 60 times per second for 30 seconds • Laptop computer to save data (1800 samples per transductor) • Laptop computer running a SCP to control power supply current • HSTA bit 0x4000 needed to be cleared to allow independent setting of supplies

  4. Test Performed • Set the boost supply to 2.5, 5.0, 7.5, 10.0, 12.5, 15.0, 17.5 and 20.0 amps (8 setpoints) • Set the bulk supply to 0, 5, 10, 15, 20, 25, 30, 35, 40 , and 45 amps (10 setpoints) • Read 30 seconds of data at the 80 different combinations • Used Excel to combine bulk and boost currents, subtract 30 second average, and calculate absolute RMS noise • Absolute RMS noise divided by average current and plotted as relative RMS noise

  5. Summary • The current linac quad power supplies should be able to meet the 0.05% noise requirement • This is more then 100 times the typical noise (<0.0005%) on new installations using switchmode power supplies and zero flux transductors Data files available @ U:\m\macnair\public\Reg29

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