Discussion about THz sources for H̄ deexcitation

Tuesday 15 Mar 2022, 11:00 → 12:30 Europe/Zurich

• Presentation by Tim on the effect of smaller THz light BW on the performance of the deexcitation
  • performance (GS fraction in same time frame) is reduced by only a factor ~2 with only 5% of the BW for each transitions from n=20 down to n'=5
  • spectral power density is higher since the total power is kept contant
  • To do:
    • look at n=30 down - frequency 200 GHz-1THz which is the range we are interested to generate now : this will require setting up a VM
    • make simulations with reduced power together with reduced BW. With and without RF
       
• Comments by JF on the typical deexcitation times
  • few 10s of us is what is required to deexcite. If can be extended to a few ms it increases the number of H̄ addressed. This is not the typical time scales considered for spectroscopy. So we could possibly increase the peak power. Some tests were done for pseudo continuous jet generation. In general, thermal time constants of the THz emitters are very small due to the smallness of the devices (typically 10x10 um) so probably cannot improve much (won't change the damage threshold but maybe the long-term robustness)
  • required duty cycle is very small. one shot every several seconds or even several tens of minutes
     
• Updates by JF:
  • no answer from the Berlin group yet

  • Colleague of JF, E. Peytavit remembered an old ANR -DFG project where TEM- horn antennas where developed. For a particular 3D design with 5um (usually - 1 um) thick LTG-GaA  the response was
    flatter in the 0.2-1THz range and absolute power value higher than standard dipoles
    JF will try to find samples to check absolute powers which were never measured. Few hundreds of uW might be possible.
    The design could be more robust because of better thermal conduction to the substrate which enables increased voltage on the structure (~50V) 
     

• Comments on THz pyrosensor

  • frequency of the chopper should not be very high (pyro are low - so typically  around a few tens of Hz) but stable for LIA to work well

  • the SLT is not provided with a LIA 

 

11:00 → 11:20 Simulation of deexcitation process with THz (n=20->5)

Speaker: Tim Hilmar Wolz (CERN)

Some_more_deexcitation_Tim_14_03_2022.pdf