Rod%20Power%20Line%20Low-Pass%20Filter%20Study

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Rod Power Line Low-Pass Filter Study
3 August 2004 Sam Burke UCSB HEP Group
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Progress

• Noise on CERN Rod Test System
• Power line is source per battery tests
• 2.5 mV _at_ 1Mhz measured on Rod PS _at_UCSB
• Low Noise on UCSB Rod System
• 1 - 2 A/D Counts

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Progress

• Inject Noise into UCSB system
• introduce noise pulse train into 0.1 ohm resistor
  placed at common power supply point and observe
  system response.
• Fixture currently being prepared for test
• Reduce self-induced noise with filtering
• Place Low Pass Filter on power line
• Shaper Noise Band Defined
• 1/260ns 4Mhz to 1/40ns 25Mhz
• gt60dB attenuation in shaper band

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Low Pass Filter Schematic
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LP Filter Response
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LP Filter Test Results
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LP Filter

• Break 2 power lines and common line and insert
  filter.

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Open Filter Issues

• Voltage drop
• VgndIR19A4.9mohms93mV on Gnd
• V2.5IR12A4.9mohms60mV on 2.5V line
• Heat Generation
• I2R192.0049ohms1.7 watts on Gnd coil
• I2R122.00490.7 watts on 2.5V line coil
• I2R72.00490.24 watts on 1.25V line coil
• Core Saturation in Machines Magnetic Field
• Open core may saturate in field
• Investigate toriod candidate

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Alternate Filter Approach

• Move filter outside of CMS magnetic enviornment
• No saturation of filter inductors
• Need to insert (splice) filter into Rod Power
  Cables
• Reduce heat generation by filter I2 heating
• Use lower winding resistance with a reduced noise
  attenuation if acceptable

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Alternate Inductor Impact
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Rod LP Filter Prototype

• High Current Inductors are on the two DC Power
  lines.
• Twisted pairs are power sense lines and analog
  sensor lines

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LP Filter At Rod Pwr Line
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Pulse Transformer
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Rod Module 1

• Top Noise injection of 10 ns pulse, 30 mhz,
  10vpk
• Bottom Low Pass Filter in Power Circuit

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Rod Module 3 (under CCU)

• Top Noise injection of 10 ns pulse, 30 mhz,
  10vpk
• Bottom Low Pass Filter in Power Circuit

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Rod Module 6

• Top Noise injection of 10 ns pulse, 30 mhz,
  10vpk
• Bottom Low Pass Filter in Power Circuit

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Future Plans