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The barrel section of the novel MIP Timing Detector (MTD) will be constructedas part of the upgrade of the CMS experiment to provide a time resolution forsingle charged tracks in the range of $30-60$ ps using LYSO:Ce crystal arraysread out with Silicon Photomultipliers (SiPMs). A major challenge for theoperation of such a detector is the extremely high radiation level, of about$2\times10^{14}$ 1 MeV(Si) Eqv. n/cm$^2$, that will be integrated over a decadeof operation of the High Luminosity Large Hadron Collider (HL-LHC). SiliconPhotomultipliers exposed to this level of radiation have shown a strongincrease in dark count rate and radiation damage effects that also impact theirgain and photon detection efficiency. For this reason during operations thewhole detector is cooled down to about $-35^{\circ}$C. In this paper weillustrate an innovative and cost-effective solution to mitigate the impact ofradiation damage on the timing performance of the detector, by integratingsmall thermo-electric coolers (TECs) on the back of the SiPM package. Thisadditional feature, fully integrated as part of the SiPM array, enables afurther decrease in operating temperature down to about $-45^{\circ}$C. Thisleads to a reduction by a factor of about two in the dark count rate withoutrequiring additional power budget, since the power required by the TEC isalmost entirely offset by a decrease in the power required for the SiPMoperation due to leakage current. In addition, the operation of the TECs withreversed polarity during technical stops of the accelerator can raise thetemperature of the SiPMs up to $60^{\circ}$C (about $50^{\circ}$C higher thanthe rest of the detector), thus accelerating the annealing of radiation damageeffects and partly recovering the SiPM performance.

Integration of thermo-electric coolers into the CMS MTD SiPM arrays for operation under high neutron fluence