The K527 linear cooler was developed in order to meet the requirements of reliability, cooling power needs and versatility for a wide range of applications such as hand held, 24/7 and MWS. During the recent years the cooler was incorporated in variety of systems. Some of these systems can be sensitive to vibrations which are induced from the cooler. In order to reduce those vibrations significantly, a Tuned Dynamic Absorber (TDA) was added to the cooler. Other systems, such as the MWS type, are not sensitive to vibrations, but require a robust cooler in order to meet the high demand for environmental vibration and temperature. Therefore various mounting interfaces are designed to meet system requirements. The latest K527 version was designed to be integrated with the K508 cold finger, in order to give it versatility to standard detectors that are already designed and available for the K508 cooler type. The reliability of the cooler is of a high priority. In order to meet the 30,000 working hours target, special design features were implemented. Eight K527 coolers have passed the 19,360 working hours without degradations, and are still running according to our expectations.
Ricor Systems has developed a compact, single stage cryopump that fills the gap where GM and other type cryopumps can't fit in. Stirling cycle technology is highly efficient and is the primary cryogenic technology for use in IR, SWIR, HOT FPA, and other IR detector technology in military, security, and aerospace applications. Current GM based dual stage cryopumps have been the legacy type water vapor pumping system for more than 50 years. However, the typically large cryopanel head, compressor footprint, and power requirements make them not cost and use effective for small, tabletop evaporation / sputtering systems, portable analysis systems, and other systems requiring small volume vacuum creation from medium, high, and UHV levels. This single stage cryopump works well in-line with diffusion and molecular turbopumps. Studies have shown effective cooperation with non-evaporable getter technology as well for UHV levels. Further testing in this area are ongoing. Temperatures created by Stirling cycle cryogenic coolers develop a useful temperature range of 40 to 150K. Temperatures of approximately 100 K are sufficient to condense water and all hydrocarbons oil vapors.
The modern needs of the electro-optical market for small low-power and light-weight IR systems are impelling research and development of High Operating Temperature (HOT) IR detectors, requiring development of dedicated “HOT” cryocoolers. The development of cryocoolers with emphasis on the “SWAP3” configuration means small size, low weight, improved performance, low power consumption and low price, in order to optimize IDDCA for future hand held thermal sights. This paper will present the development and the progress made with the new "HOT" cryocooler, including customer data after the evaluation process, performances achieved using a common cold finger, test results update on a large series of production coolers, life and qualification test update and acoustic noise reduction. All the above mentioned information relates to the FPA temperature range of 130 - 200K for various cryocooler models based on rotary and linear design concepts. The paper will also review the progress with the latest development activities implemented in the cryocoolers and the electronic control modules in order to improve reliability and minimize regulated power consumption.
Early rotary cryocoolers were designed for the lifetime of a few thousands operating hours. Ricor K506 model’s life
expectancy was only 5,000 hours, then the next generation K508 model was designed to achieve 10,000 operating hours
in basic conditions, while the modern K508N was designed for 20,000 operating hours.
Nowadays, the new challenges in the field of rotary cryocoolers require development of a new generation cooler that
could compete with the linear cryocooler reliability, achieving the lifetime goal of 30,000 operating hours, and even
Such new advanced cryocooler can be used for upgrade existing systems, or to serve the new generation of high-temperature
detectors that are currently under development, enabling the cryocooler to work more efficiently in the field.
The improvement of the rotary cryocooler reliability is based on a deep analysis and understating of the root failure
causes, finding solutions to reduce bearings wear, using modern materials and lubricants. All of those were taken into
consideration during the development of the new generation rotary coolers.
As a part of reliability challenges, new digital controller was also developed, which allows new options, such as discrete
control of the operating frequency, and can extend the cooler operating hours due to new controlling technique. In
addition, the digital controller will be able to collect data during cryocooler operation, aiming end of life prediction.
The growth in world demand for infrared missile warning systems (MWS) has impelled the development of new technologies, in particular, special ruggedized cryogenic coolers. Since the cryocooler is a core component in ruggedized platforms, RICOR has met the challenge by developing new models able to withstand high ambient temperatures above 110°C, as well as harsh vibration levels, both derived from airborne fighter applications. One of the development efforts focused on a cryocooler regenerator and cold finger optimization, in order to achieve high cooling capacity at 95K FPA and the efficiency of about 5.3 % at 102 °C.
In order to withstand harsh environmental vibration and high ambient temperature range, the mechanical parts of the cryocoolers were designed and tested for a high structural safety factor along with weight minimization. The electronic design concept was based on encapsulated controllers, the PCB of which has been designed with internal heat sinking paths and special components able to withstand ambient temperatures of up to 125°C.
As a final stage of development, four cryocooler models (K544, K549, K527 and K508) were successfully qualified under harsh environmental conditions, both by RICOR and by system manufacturers. Also life demonstration tests were performed with these models. The cryocoolers were designed and tested successfully to meet requirements of military standards MIL- STD-704D, MIL-STD- 461E and MIL-STD-810F reflecting real mission profiles in harsh environment.
The world growth in research and development of High Operating Temperature (HOT) IR detectors impels development and optimization of suitable cryocoolers. The current developments at RICOR are focused on the SWAP-oriented design process, meaning small Size, low Weight and low Power consumption, providing proper cryocoolers for future hand held thermal imagers.
This paper shows the progress made during development of "HOT" cryocooler prototypes, and engineering preproduction series cryocoolers working at the FPA temperature range of 130 - 200K. Three different cryocooler models based on rotary & linear design concepts are presented below. The progress with development of electronic control modules providing minimized regulated power consumption is also shown.
The world growth in research and development of High Operating Temperature IR detectors impels the development process and the optimization of HOT Cryocoolers at RICOR. The development emphasizes the “SWaP” configuration which is Small Size, Low Weight and Low Power consumption, in order to optimize IDDCA for future hand held thermal sights and other various applications. This paper will present optimization tests results performed on HOT Lab Demonstration Cryocoolers at the temperature range of 130 - 180K FPA and also will review the development activities that will be implemented in order to minimize "Idle electronic and mechanical losses", hence minimizing the regulated power consumption. The new Cryocoolers developed for HOT detectors aim for higher reliability which is analyzed and reported in the paper.
The authors summarize the results of the accelerated life testing of the Ricor type K529N 1 Watt linear split Stirling cooler. The test was conducted in the period 2003-2006, during which the cooler accumulated in excess of 27,500 working hours at an elevated ambient temperature, which is equivalent to 45,000 hours at normal ambient conditions, and performed about 7,500 operational cycles including cooldown and steady-state phases. The cryocooler performances were assessed through the cooldown time and power consumption; no visible degradation in performances was observed.
After the cooler failure and the compressor disassembling, an electrical short was discovered in the driving coil. The analysis has shown that the wire insulating varnish was not suitable for such elevated temperatures. It is important to note that the cooler under test was taken from the earliest engineering series; in the later manufacturing line military grade wire with high temperature insulation was used, no customer complaints have been recorded in this instance
Special attention was paid to the thorough examination of the technical condition of the critical components of the cooler interior. In particular, dynamic piston-cylinder seal, flying leads, internal O-rings and driving coil were examined in the compressor. As to the cold head, we focused on studying the conditions of the dynamic bushing-plunger seal, O-rings and displacer-regenerator. In addition, a leak test was performed to assess the condition of the metallic crushed seals.
From the analysis, the authors draw the conclusion that the cooler design is adequate for long life performance (in excess of 20,000 working hours) applications.