Luis F. Delgado-Aparicio 1, M. Bitter 1, N. A. Pablant 1, K. Hill 1, J. Rice 2, Y. Podpaly 2, M. L. Reinke 2, J. R. Wilson 1, D. Johnson 1 Real-time temperature feedback on HiReX-Sr ① Motivation: HiReX-Sr can experience temperature excursions as much four degrees due to the non- reproducible conditions of the test- cell temperature. ② Goal: Eliminate the crystal temperature excursions or stabilize the crystal temperature through real-time temperature feedback. ③ Background: Any change in the interplanar spacing will result in an apparent measurement of a non-zero velocity:

New off-the-shelf electronics allows heating and control of spectrometer housing at 30 ±0.1 ℃ ① Local area network. ② Individual K-type ther- mocouples sense the heating-pad tempera- tures and activate the feedback process. ③ CNi16D44-C24 con- troller with C4EI option for slaving up to 32 devices through MOD- BUS RS-485 protocol. Pulse width output (duty cycle: 0→0.99) ④ Solid state relays (duty cycle control: capable up to 25 Amps). ⑤ Diode limiting the current and power dissipated (no full use of ~5W/in 2 capability). ① ② ③ a) b)c)d)e) ① ③ ④ ⑤ ②

New in-situ temperature sensing & feedback systems can be controlled/adjusted remotely ① 8-channel ethernet- based power strip. ② Remotely controlled unit capable of sensing and “tuning” the individual temperatures of the thermal pads according to programmable set- points. Elements ③ Data acquisition switch/multiplexer unit allowing sensing of five 4-wire flexible-molded resistive temperature devices (RTDs) monitors placed inside HiRex-Sr. Real-time data will also be available in the C-Mod data archive tree. ① ② ③