Barak Moshe & Avishai Filis, Nachman Pundak, Zvi Bar Haim, Givon Cohen Eyal

RICOR – Cryogenic & Vacuum Systems, En Harod Ihud 18960, Israel

 ABSTRACT

 The growing demand for EO applications that work around the clock 24hr/7days a week, such as in border surveillance, emphasizes the need for a highly reliable cryocooler from maintenance considerations and Life Cycle Cost calculations. As a result, RICOR developed a new rotary Stirling model K508N with a main design goal of 20,000 operating hours, double the operating hours performance of the standard K508 model.

The secondary goal of the K508N model is to maintain K508 cryogenic performances while keeping all the electrical and mechanical interfaces of the standard K508 so as to enable full interchangeability with a standard K508 for retrofit and for new projects as well. The K508N includes RICOR’s latest mechanical design technologies such as optimized bearings and greases, internal parts arrangement and preloading, advanced seals, advanced plating for external parts, a laser welded cold finger and robust design structure with increased natural frequency compared to the K508 model.

Also included in the K508N is an improved on board analog controller based on a single PCB that contains a controller and motor driver based on the logic of the time-tested Hyb18N. In the next step, an on board digital controller will be implemented as a derivative of the qualified external controller board used with RICOR’s K562S model. The K508N is designed to be fully RoHS compliant, mechanically and electronically as well. The Cooler MTTF is evaluated by a theoretical reliability study and is also demonstrated by a comparative accelerated life test between three standard K508 coolers and three K508N coolers.

This paper also includes intermediate results form the accelerated life test. The K508N is designed for orientation with future EO needs such as high reliability, RoHS compliance, robustness, a digital controller, in order to provide the foundations of future EO systems.

Keywords:  Cryocooler, Stirling, Reliability, Long Life, MTTF, RICOR, Electro Optics, Life Cycle Cost.

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