The Measurement of a Lepton-Lepton Electroweak Reaction (MOLLER) experiment anticipates
new dynamics beyond the Standard Model. The measurements are acquired by the scattering of
longitudinally polarized electrons off unpolarized electrons in a liquid hydrogen target using a set of
detectors in Hall A at the Thomas Jefferson National Accelerator Facility (JLab) in Newport News,
Virginia, USA. MOLLER will use High Voltage-Monolithic Active Pixel Sensors (HV-MAPS) in
the Hall A’s Compton polarimeter to monitor the polarization. The detector contains a quad-planar
geometry and each plane has three HV-MAPS chips attached. Compton polarimeter requires the
HV-MAPS to be placed inside the vacuum to allow for the detection of the scattered electrons. The chips generate heat during operation, and thus require an effective cooling
system. The temperature measurement of the HV-MAPS in vacuum is essential to understand the
thermal properties of the pixel detector and cooling needs. This project reviews the efforts towards
the cooling strategies, structure modification, and thermal simulations to achieve an in-vacuum
operation. Further, the prototyping and successful testing of the electron detector’s cooling system
(using a test version of HV-MAPS chips with equivalent heat load) in a local lab was performed,
and computational fluid dynamics studies are compared with the collected data.