Toroidal Axion Haloscope Development at CAPP Harry W Themann Center for Axion and Precision Physics Daejeon, ROK LLNL-Microwave Cavity Workshop 2017 1/11/2017 Harry W Themann CAPP 1
Why Toroid? π β π π·πΆ 2 π Axion Power π β’ Larger cavities, higher field magnets, preserve Q & C β’ Larger cavities -> problem at higher frequencies β’ Multiple Cavities (see SW Youn) β’ What about Toroids? β’ No endcaps, can I get something for nothing? β’ With a toroidal magnet the πΆ field is, at least nominally, parallel to all conductive surfaces β’ Lends itself to superconductive films? 1/11/2017 Harry W Themann CAPP 2
Toroid Modes β’ No pure TM or TE modes β’ Inverse toroid aspect ratio π 0 = π π β’ Bicycle tubes are better than truck tubes β’ πΉ field lines of desired mode similar to applied B field β’ No mode crossings 1/11/2017 Harry W Themann CAPP 3
Analytic Modes β’ Cap and Deutsch lEEE Transactions on Microwave r Theory and Techniques Vol MTT-26,NO.7, JULY1978 β’ Janaki & Dasgupta IEEE Transactions on Plasma Science, VOL. I X . NO. I . FEBRUARY 1990 π π β’ Inverse toroid aspect ratio π 0 = β’ J & D expand in π 0 R β β β’ ππ "ππππ" β π=0 π π TM + π=0 π π TE β’ As π β β π 0 β 0 ππ "ππππ" πππππππ‘ ππ β’ For the dimensions contemplated there are no degeneracies, no crossings β’ We used simulation to verify this 1/11/2017 Harry W Themann CAPP 4
Effective Volume B 2 VC B. R. Ko; Axion Dark Matter Workshop, Stockholm 1/11/2017 Harry W Themann CAPP 5
Low Fringe Fields R = 200cm R = 50cm B avg = 5T 9 coils 1/11/2017 Harry W Themann CAPP 6
Q Factor B. R. Ko; Axion Dark Matter Workshop, Stockholm 1/11/2017 Harry W Themann CAPP 7
Assembly Concept 1/11/2017 Harry W Themann CAPP 8
Assembly Concept 1/11/2017 Harry W Themann CAPP 9
Assembly Concept 1/11/2017 Harry W Themann CAPP 10
First Toroid βSUBβ β’ Driven by a desire to be able to mount in a cryocooler available to us β’ R=4cm r=2cm π 0 = 0.5 β’ Simulation verifies no mode crossing 1/11/2017 Harry W Themann CAPP 11
Cappuccino βSUBβ β’ Early iteration of design β’ Simulation β’ Dimensions of SUB β’ Dimensions of tune hoop β’ Antenna sizes and shapes β’ Antenna placement (we had them at angles in the beginning) 1/11/2017 Harry W Themann CAPP 12
Design Challenges β’ Three sections not necessary for this model but we decided to have a learning experience β’ One challenge was to exert force to push ends together 1/11/2017 Harry W Themann CAPP 13
Photo 1/11/2017 Harry W Themann CAPP 14
CAD Pictures 1/11/2017 Harry W Themann CAPP 15
First Look β’ Coupling issues, cross talk with each other with hoop, sim vs data β’ Best antenna shape/size, reality vs simulation β’ Q factor β’ Calculated 20 000 β’ Alignment issues, best 6000 β’ Indium βgasketsβ were a failure β’ Bagel cut achieved 20 000 w/o hoop β’ The simulations predicted that the hoop must go upwards but doesnβt seem to matter 1/11/2017 Harry W Themann CAPP 16
Finished Product 1/11/2017 Harry W Themann CAPP 17
Q = 10,700 CF = 8.159GHz 1/11/2017 Harry W Themann CAPP 18
B. R. Ko; Axion Dark Matter Workshop, Stockholm 1/11/2017 Harry W Themann CAPP 19
Pictures 1/11/2017 Harry W Themann CAPP 20
Future 500mm Major Radius β’ Continue to develop flanging β’ Scale up tuning β’ Cryogenic ready β’ Packaging β’ Physical placement β’ Placement WRT to cooling β’ Cable routing β’ Actuation routing 1/11/2017 Harry W Themann CAPP 21
Conclusion β’ We have a working toroidal cavity β’ Learned a lot but this has also made us realize that there are some daunting challenges in front of us. β’ CAPP LVP Hall is building momentum rapidly 1/11/2017 Harry W Themann CAPP 22
BACKUP 1/11/2017 Harry W Themann CAPP 23
Assembly Concept 1/11/2017 Harry W Themann CAPP 24
Challenges 1/11/2017 Harry W Themann CAPP 25
1/11/2017 Harry W Themann CAPP 26
1/11/2017 Harry W Themann CAPP 27
1/11/2017 Harry W Themann CAPP 28
B. R. Ko; Axion Dark Matter Workshop, Stockholm 1/11/2017 Harry W Themann CAPP 29
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