I suppose this ‘Leitung’ means control, then, Beam Loss Monitoring (BLM) system (https://inspirehep.net/record/775962)
Als Kryostat (griechisch κρύος ‚kalt‘) wird ein Kühlgerät bezeichnet, mit dem sehr tiefe Temperaturen erreicht und konstant gehalten werden können. - https://de.wikipedia.org/wiki/Kryostat
A cryostat (from cryo meaning cold and stat meaning stable) is a device used to maintain low cryogenic temperatures of samples or devices mounted within the cryostat. - https://en.wikipedia.org/wiki/Cryostat

line cryostat losses / power transmission cryostat losses

sources:

What is line loss? definition and meaning - BusinessDictionary.com
www.businessdictionary.com/definition/line-loss.html
Definition of line loss: Waste of electrical energy due to inherent inefficiencies or defects in the distribution or transmission system.

Leitungsverlust | Übersetzung Englisch-Deutsch - dict.cc
https://www.dict.cc/?s=Leitungsverlust
dict.cc | Übersetzungen für 'Leitungsverlust' im ... Deutsch-Englisch-Übersetzung für: Leitungsverlust. DE <> EN, DE –> EN ... tech. line loss · Leitungsverlust {m} ...

Electric power transmission and distribution losses (% of output) | Data
https://data.worldbank.org/indicator/EG.ELC.LOSS.ZS
Electric power transmission and distribution losses (% of output) from The World Bank: Data.

Electric power transmission losses - Learn what is efficiency of power ...
https://www.brighthubengineering.com/power.../42429-power-lo...
This gives rise to the concept power transmission efficiency which is an important figure as it gives an idea of the losses during transmission of electricity.

Reducing Electricity Transmission Loss - Beta Engineering
www.betaengineering.com/.../reducing-electricity-transmissi...
Ohmic loss refers to Joule heating loss when electricity encounters resistance in transmission line conductors.

Energy losses of superconducting power transmission cables in ...
https://www.researchgate.net/.../224070002_Energy_losses_of_... -
PDF | One of the obvious motives for development of superconducting power transmission cables is reduction of transmission losses. Loss components in ...

Superconducting Cable - an overview | ScienceDirect Topics
https://www.sciencedirect.com/topics/.../superconducting-cab... -
Using superconducting DC cables to improve the efficiency of electricity transmission and distribution (T&D) ... Cable and cryostat losses at 20 K, ∼120 W.

Advances in Cryogenic Engineering
https://books.google.com/books?isbn=1461398568 -
K. D. Timmerhaus - 2013 - ‎Science
The measured cryostat losses of the compensating coil system A were within ... tank increased to the blowdown pressure of the first stage of the safety line (4 bar ...

Cryostat Optimization Through Multiple Stage Thermal ...
https://www.academia.edu/.../Cryostat_Optimization_Through_M...
[2] For transmission applications, the cryostat losses are dominated by distributed thermal loads, as the losses in the current terminations are small compared ...

Advances in Superconductivity XI: Proceedings of the 11th ...
https://books.google.com/books?isbn=4431668748 -
N. Koshizuka, ‎S. Tajima - 2013 - ‎Technology & Engineering
Proceedings of the 11th International Symposium on Superconductivity (ISS '98), ... exactly because of other heat load (e.g. the cryostat losses, AC losses, etc.) ...

I was inclined towards "cryostatic line losses" or cryostatic transmission losses.
However I couldn't find any instance of those phrases being used in real life.

I did, however, find an instance of "cryogenic line losses" used in a 2015 academic journal article (vide infra). Hence "cryogenic transmission losses" also may be feasible.

I wouldn't say that "cryogenic" and "cryostatic" are perfect synonyms, but in some contexts they may be interchanged.

Cryogenic Design of the 43 T LNCMI Grenoble Hybrid Magnet:
"The cryogenic line losses are 4.5 W at 1.8 K, 4.5 W at 4.5 K and 28.2 W at 77 K, respectively. 7. The Eddy Current Shield (ECS) The ECS is adapted from the former SC magnet [1], [8], [9], [10]."
https://doi.org/10.1016/j.phpro.2015.06.117