CHARACTERIZATION AND OPTIMIZATION OF PREAMPS FOR THE MU2E TRACKER P E R I A N N E J O H N S O N S I S T I N T E R N , F N A L P P D N E W M E X I C O I N S T I T U T E O F M I N I N G A N D T E C H N O L O G Y 1 4 August 2014 PERIANNE JOHNSON
OVERVIEW • General Background on Mu2e • Preamp Specifications • Original Preamp • Modifications • New Design • Future Improvements 2 4 August 2014 PERIANNE JOHNSON
MU2E: CHARGED LEPTON FLAVOR VIOLATION Neutrinoless conversion of a muon into an electron • Rare event – rates predicted by SM theory of < 10 -50 • Effectively, one event could imply New Physics • 3 4 August 2014 PERIANNE JOHNSON
MU2E: STRAW TRACKER • 5 mm mylar straw with wire running through it, potential difference draws ionized ArCO 2 to wire, creating current • Array tracks path of particles • Preamp at each end – distance determination 4 4 August 2014 PERIANNE JOHNSON
PREAMPS: BASICS Small printed circuit board (4.0 by 1.1 cm by 31 mils) • Amplifies an input signal at an inherent gain • 𝐻 𝐻𝑏𝑗𝑜↓𝑒𝐶 =20 =20 lo log ↓ 10 10 (𝐵 (𝐵↓𝑝𝑣𝑢 /𝐵 𝐵↓𝑗𝑜 ) ) 5 4 August 2014 PERIANNE JOHNSON
PREAMPS: SCHEMATIC Bala lanc nce Point nt 6 4 August 2014 PERIANNE JOHNSON
PREAMPS: MOTHERBOARD Provides power, programming via 1-Wire, and viewing of output signal for eight preamps • Mounted very close together – cross talk • 1-Wire C Chi hips Arduino no Scope Sc pe Conne nnector Cable les Cha hanne nnels ls 7 4 August 2014 PERIANNE JOHNSON
PREAMPS: PROGRAMMING One Wire Chip – 8 Channel Addressable Switch • Arduino Due Microcontroller • Python • 8 4 August 2014 PERIANNE JOHNSON
PREAMPS: “READ.PY” Time (ns ) 4 August 2014 9 PERIANNE JOHNSON
ORIGINAL PREAMPS • No shaping • Soldered directly to motherboard • 2.5 mV input peak-to-peak amplitude from signal generator 4 August 2014 10 PERIANNE JOHNSON
ORIGINAL PREAMPS: CROSS TALK • Unavoidable fact of close mounting • Mounted second preamp into channel 6 on motherboard • Two percent limit for final experiment 11 4 August 2014 PERIANNE JOHNSON
NEW PREAMPS: SHAPING • Addition of 100 pF capacitor to shape (“boost”) gain at 100 MHz • Factor of five increase • Input Signal: 50 mV attenuated by 38 dB – 0.63 mV 12 4 August 2014 PERIANNE JOHNSON
INSTABILITY: REMOVAL OF CAPACITOR • Boosting made the preamps very sensitive to movement / touching • Touching preamps adds capacitance where it doesn’t belong • Shaping capacitor was removed from eight preamps Preamp # ¡ Balance # ¡ Voltage Drop ¡ Output Amplitude (mV) ¡ Noise RMS ¡ 0 ¡ 22800 ¡ 70 ¡ 21 ¡ 0.35 ¡ 1 ¡ 22600 ¡ 74 ¡ 23 ¡ 0.38 ¡ 2 ¡ 22900 ¡ 65 ¡ 48 ¡ 0.6 ¡ 3 ¡ 22400 ¡ 74 ¡ 21 ¡ 0.34 ¡ 4 ¡ 22300 ¡ 75 ¡ 21 ¡ 0.36 ¡ 5 ¡ 23100 ¡ 70 ¡ 24 ¡ 0.36 ¡ 6 ¡ 21800 ¡ 73 ¡ 20 ¡ 0.33 ¡ 7 ¡ 22300 ¡ 71 ¡ 22 ¡ 0.35 ¡ 13 4 August 2014 PERIANNE JOHNSON
INSTABILITY: BFP520 VERSUS BFP720 • Originally, two 720s for input and three 520s for output • BFP720: Si-Ge material allows for faster transition frequency and greater bandwidth • Via not well grounded – small piece of copper tape 14 PERIANNE JOHNSON 4 August 2014
BFP 520 + COPPER TAPE 15 4 August 2014 PERIANNE JOHNSON
BETTER GROUNDING FOUND • Large ground plane right by components that rely on via • Flipped them around and soldered, now well grounded 16 PERIANNE JOHNSON
FINAL PREAMPS: GAIN • All BFP520 transistors, shaping capacitor replaced, components flipped to ground 17 4 August 2014 PERIANNE JOHNSON
FINAL PREAMPS: CROSS TALK • Above the requisite two percent, no further testing done at this point 18 4 August 2014 PERIANNE JOHNSON
CONCLUSIONS & FUTURE MODIFICATIONS • 52 db gain for preamps with: - BFP520 transistors throughout - Shaping capacitor - Better grounding • Original preamps: gain of 30 dB • Future Modifications: - Better grounding for components built into layout - Reduction of cross talk to signal ratio 19 4 August 2014 PERIANNE JOHNSON
QUESTIONS? 20 4 August 2014 PERIANNE JOHNSON
REFERENCES DS2408: 1-Wire 8-Channel Addressable Switch http://www.maximintegrated.com/en/products/digital/memory-products/ DS2408.html Arduino Due Microcontroller http://arduino.cc/en/Main/ArduinoBoardDue 21 4 August 2014 PERIANNE JOHNSON
ACKNOWLEDGEMENTS Several parties are deserving of recognition for the success of this project and summer internship. I would first like to thank my supervisor, Dr. Vadim Rusu, for providing me with ample guidance and support throughout my project, while also allowing me to learn from my own mistakes. I would also like to thank my assistant supervisor, Aseet Mukherjee, and coworker Angela Yang for always lending her third hand. Finally, I would like to recognize Elliot McCrory, Dianne Engram, Linda Diepholz and the rest of the SIST Committee for selecting me to be a part of this program. 22 4 August 2014 PERIANNE JOHNSON
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