Stark deceleration methods for cold molecule experiments by Yomay Shyur B.A., Wellesley College, 2011 M.S., University of Colorado Boulder, 2014 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Physics 2018 This thesis entitled: Stark deceleration methods for cold molecule experiments written by Yomay Shyur has been approved for the Department of Physics Prof. Heather Lewandowski Prof. John Bohn Date The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. iii Shyur, Yomay (Ph.D., Physics) Stark deceleration methods for cold molecule experiments Thesis directed by Prof. Heather Lewandowski The growing field of cold molecule physics has demonstrated many methods of quantum control for precision measurement and molecular interaction studies. One particular method is Stark deceleration, which uses electric field gradients to produce packets of slow polar molecules. Since Stark deceleration does not increase phase-space density, the efficiency of the deceleration process is critical in determining the final cold molecule density. This dissertation describes three different Stark deceleration techniques. The first type of deceleration is pulsed-pin deceleration. We use this technique to produce slow OH molecules that can be trapped for cold collision studies. A two photon state-selective detection system, which includes a 118 nm photon, is used to determine the density distribution of OH in the trap. We explore the advantages and limitations to creating 118 nm light. The second and third types of Stark deceleration are pulsed-ring and traveling-wave methods of running a ring-geometry decelerator. Ring-geometry decelerators present improved deceleration efficiencies due to the cylindrical symmetry of the electrodes and true three-dimensional confine- ment. The pulsed-ring mode of the ring decelerator uses commercial high-voltage switches to apply discrete pulses to the ring electrodes. The continuous operation mode of the ring decelerator uses varying sine-wave voltages to create a traveling Stark potential well and has proven to be incredibly challenging due to the analog high voltage requirements of the system. In order to bring ND3 seeded in krypton (∼415 m/s) down to rest in the laboratory, sine wave voltages with amplitudes up to ±10 kV, currents up to 500 mA, and a bandwidth of 30 kHz down to DC are required. We describe a high-voltage amplifier that can be used for traveling-wave deceleration. The traveling-wave Stark deceleration mode is then compared to the pulsed-ring Stark deceleration mode and cases where one mode is superior to another are discussed. Dedication To my parents. Acknowledgements It is a pleasure to thank the people whose many efforts have made this dissertation possible. First, I would like to thank my advisor, Heather Lewandowski. She believed in me and entrusted me with an electronics project when I had very little background coming in. She always provided encouragement even when amplifier land seemed endless and bleak. She has been a patient mentor, who has taught me how to tell a story using data and brainstorm solutions to a myriad of scientific problems. All these skills will serve me well in future endeavors. I also owe my gratitude to all the Lewandowski lab members I have worked with. Each one of you has taught me so much. Noah Fitch had the ambition to embark on the high-voltage amplifier journey, and provided valuable documentation and help even after moving to Europe. His groundwork in design, construction, and simulations for the ring decelerator have been critical to its operation. Travis Briles taught me a lot about optics and lasers and could provide references for seemingly endless cold molecule topics. Maya Fabrikant was always eager to help solve problems both in the lab and outside of lab. The construction of the ring decelerator and amplifiers would not have been possible without the work of David Macaluso, Kentaro Hoeger, and Ian Collett. I have also had the pleasure of working with John Gray and Jason Bossert, their eagerness to work on challenging experiments, persistence in finding the root of the problem, and ability to keep things upbeat in the lab have been invaluable. I wish both of them the best of luck as they continue their work on collision and reaction experiments. Additionally, help from and conversations with Philipp Schmid, James Greenberg, Kyle Miller, Cameron Straatsma, and Ben Saarel have been incredibly useful. vi I have greatly benefited from discussions with the JILA cold molecule community. In partic- ular, David Reens and Hao Wu have always provided keen insights into OH and Stark decelerator improvements. The construction, upkeep, repair, and upgrades to these mechanically and electron- ically complex decelerator experiments would not have been possible without the help of the JILA machine and electronics shops. Specifically, Terry Brown from the electronics shop deserves special recognition for the initial design of the amplifiers and many subsequent discussions. Before embarking on my journey at JILA, I had many professors and mentors who encouraged me and guided me. I am thankful of the Wellesley College physics community where I have always found a home and Glenn Stark who gave me international physics research experience in my first year at Wellesley. Recognition also goes to Chris Arumainayagam, Juliet Pickering, Gillian Nave, and Gretchen Campbell who opened up their labs to me so that I could learn new things. Thanks also goes out to Catherine Klauss, the best roommate ever, and my friends in Boulder for all the ski trips, cooking endeavors, encouragement, and support. And to my friends from afar, particularly Amanda and Rachel, who checked in regularly and were always interested in what was going on in the lab. Lastly, I wish to thank my parents for their endless encouragement, without their support I would have never taken this journey. Contents Chapter 1 Introduction 1 1.1 Molecules in electric and magnetic fields . .3 1.2 Beam Manipulation Techniques . .5 1.3 Outline of this dissertation . .7 2 Stark Deceleration 9 2.1 Applications of Stark Decelerators . .9 2.1.1 Pin decelerators . 10 2.1.2 Ring decelerators . 12 2.1.3 Other Stark related techniques . 14 2.2 Stark Decelerator Operation . 15 2.2.1 Pulsed-pin Stark deceleration . 15 2.2.2 Traveling-wave Stark Deceleration . 24 2.2.3 Pulsed Ring Stark Deceleration . 28 2.3 Phase-space Acceptance . 28 2.4 Simulations . 36 2.5 Experimental Layout . 39 2.5.1 Supersonic Expansion . 41 2.5.2 Detection . 43 viii 2.5.3 Our experiments . 45 2.6 Decelerator comparison . 52 3 Molecules of Interest 55 3.0.1 Rotational states . 57 3.1 Ammonia . 59 3.1.1 Stark effect in ND3 ................................. 60 3.1.2 ND3 REMPI . 61 3.2 OH.............................................. 62 3.2.1 Hund's Coupling Cases . 62 3.2.2 OH structure . 64 3.2.3 OH in electric fields . 65 4 Pulsed Ring Stark Deceleration 67 4.1 Pulsed-Ring versus traveling-wave Stark deceleration . 67 4.1.1 Introduction . 67 4.1.2 Experiment . 71 4.1.3 Simple model of deceleration . 74 4.1.4 Simulations . 77 4.1.5 Experimental Results and Analysis . 78 4.1.6 Conclusion . 85 4.2 Implementing PRSD . 86 4.3 Decelerating with PRSD . 90 4.4 Transverse Dynamics . 94 4.5 Calibration . 97 4.6 8-ring periodicity PRSD . 101 ix 5 High-Voltage Amplifiers 105 5.1 High-Voltage Amplifier Electronics . 106 5.1.1 Introduction . 106 5.2 Design of the high-voltage amplifier . 109 5.2.1 Leader Stage . 111 5.2.2 Follower Stages . 114 5.2.3 Feedback and control . 116 5.2.4 Physical Construction . 118 5.3 Amplifier Performance . 121 5.3.1 Testing Setup . 121 5.3.2 General Specifications . 122 5.3.3 Voltage Sharing . 127 5.3.4 Chirped sine waves . 129 5.4 Conclusion . 130 5.5 Individual amplifiers . 130 5.6 Insulation . 134 5.6.1 Amplifier bank . 134 5.6.2 Amplifier walls . 143 5.6.3 Optoisolator Failures . 145 5.7 Operating multiple amplifiers . 149 5.7.1 Digital and analog signals . 149 5.7.2 Master Interlock . 153 5.7.3 Enabling amplifiers . 155 5.8 Amplifier Changes . 158 5.8.1 Component value changes . 158 5.8.2 Parts not in use anymore . 162 x 6 Electrostatic trapping of OH 164 6.1 OH experimental setup . 167 6.2 OH REMPI Detection . 172 6.3 OH 1+1' REMPI with 118 nm photons . 173 6.4 OH in electric and magnetic fields . 177 6.4.1 Hamiltonian for OH in electric and magnetic fields . 179 6.4.2 Electrostatically trapped OH with a uniform magnetic field . 180 6.4.3 Future work . 185 6.5 118 nm light . 186 6.5.1 Creating 118 nm light . ..