Emi a

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Emi a

  1. 1. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 EMI/EMC Requirements & Open Issues Design Approach Sept 2, 2003 Stanford Linear Accelerator Center Stanford CADavid Nelson Design Approach 1
  2. 2. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Design Issues (1)• Aluminum & Titanium surface preparation• Grid• RF Shield• X-LAT Plate• Radiators• Space craft• ACD• Calorimeter• Tracker• DAQ• Copper TapeDavid Nelson Design Approach 2
  3. 3. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Surface preparation (1)• Aluminum/Titanium Surface Preparation – Chem-film (Alodine)-Mil-C-5541D Class 3 • Grand fathered into systems design, everyone does it • Easy to use, Cheap • 5 milli-Ohm/in^2 • People routinely scrape off alodine to improve electrical contact.David Nelson Design Approach 3
  4. 4. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Surface preparation(2) – Electro less Nickel SAE AMS-2404 • “Gold over nickel or electro less nickel are the preferred plating for GSFC applications” PPL-21 Connectors • Easy to use, Cheap • Micro-Ohms/in^2 • Issues – Adhesion for bonding heaters/paint – Plating titanium, Dr. Stefanie Harvey from SLAC’s Physical electronics group has written a proposal to address Spectrum’s concerns.David Nelson Design Approach 4
  5. 5. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 LAT Assembly, TKR & ACD not shownRADIATORINTERFACE X-LAT Plates RFI SHIRT GRID to CAL Connector Panels David Nelson Design Approach 5
  6. 6. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Grid, RF Shield & X-LAT Plate• Grid & RF Shield – Plating • Currently no plating or Alodine • Request electro less nickel – Assembly interfaces • All joints are butted – Request tongue & grove joints » Allows for EMI gasket if needed – Vent holes • Currently four 2”X2” vent holes on EMI skirt. • Request no vent holes due to adequate venting through CAL base plate/grid/tracker towers. (TBR)David Nelson Design Approach 6
  7. 7. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Butted Joints Butted JointsDavid Nelson Design Approach 7
  8. 8. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Radiators(1)• Interface to Radiator mount – Currently G10 Thermal Insulator • Request Ti/Al/Cu shim stock wrapped around G10 to get low resistance and inductance – Heat pipes are thermally connected but not electrically • Request to include electrical connection as well – Request to shield heaters and wiring • EMI measurement shows approx 15uVdB electric field noise emitted from one six watt heater using 50mV peak 500KHz signal.David Nelson Design Approach 8
  9. 9. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Radiators(2) Radiator Radiator Mount Heat PipesDavid Nelson Design Approach 9
  10. 10. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Space craft Interface• Current design – Titanium flexures Aldine coating • Electrical resistance with Aldine is 9 milli-Ohm per Spectrum Astro – Request Electro less nickel • The 433-RQMT-0005 requires a maximum of 2.5 milli-Ohm per connection – SLAC is looking into issues of electro less nickel onto titanium, See slides 3 & 4David Nelson Design Approach 10
  11. 11. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 ACD Issues• Butted joints in BEA assembly• ACD is looking into this• Alodine – Request E-Nickel• Look at BEA mountingDavid Nelson Design Approach 11
  12. 12. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Calorimeter Issues• Current design – Alodine • Request E-Nickel – Joints are not EMI tight – Butted joints – N. Johnson stated that gaps in panels due to improper assy.• Issues – Low Freq 3.3V CMOS Switching noise escapes – Request EMI gaskets or Copper tapeDavid Nelson Design Approach 12
  13. 13. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Tracker Issues• To copper tape or not to copper tape – Issues • Calorimeter people claim that copper/aluminum tape is not allowed. – Either the Cal can or the Tracker can’t ??? » We are one system after all• EMI close out to prevent radiated EMI from DAQ and Calorimeter. – Cal base plate is an EMI sieve that can travel through the gaps between the Tracker towers. • Request the Calorimeter to shield against their low frequency 3.3V CMOS noise per slide 12 – May need additional EMI shielding between towersDavid Nelson Design Approach 13
  14. 14. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 DAQ Issues• Titanium standoffs between Cal base plate and DAQ TEM – Electro less nickel issues from slide 3&4• The EMI filters on power feeds should take care of 433-RQMT- 0005• Power feed impedance – Spectrum Astro has modified there requirements • More work• DC resistance issues between Spectrum Astro and the LAT due to voltage measurements that is referenced to LAT/system ground – Open issueDavid Nelson Design Approach 14
  15. 15. GLAST LAT Project EMI/EMC Requirements & Open Issues, Sept 2, 2003 Conductive Tape• The Calorimeter people claim conductive tape is not allowed – Either the Calorimeter can use it or the Tracker can’t ???David Nelson Design Approach 15

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