In recent years, the trend of moving IR detectors to operate from standard 77K to the High Operating Temperature (HOT) of 150K, drives RICOR’s onward development focusing on SWaP-C, a new family of miniature cryocoolers, alongside continuing to make improvements to existing cryocooler models. The main objective for the development of a new family of cryocoolers is to focus on SWap-C by creating cryocoolers that maintain a small size, low weight, low power consumption and an attractive cost. This effort has yielded advanced Linear & Rotary miniature Cryocoolers named K580, K588 and K590. This paper will review the progress made with qualification and the move to production of the K590 Linear Dual Opposed model using customized cold finger & engineering efforts to optimize the K588 model that based on the same compact dual opposed compressor integrated with a common cold finger. In addition, the paper will present the improvements made for K580I Integral Rotary Model with lower induced force level and will review the accumulated experience of 3 mature models under production named K527, K562S and K562SI.
The modern needs of the electro optical market for small low-power and light-weight IR systems are impelling development of High Operating Temperature (HOT) IR detectors, requiring development of dedicated cryocoolers. The development of cryocoolers focused on “SWAP-C” configuration means small size, low weight, low power consumption and attractive cost, in order to optimize IDDCA for modern compact thermal imagers. This paper will review the progress made with the new rotary K580 cryocooler for HOT detectors, update on qualification and life demonstration test results, present test results accumulated from production ramp-up and review the compliance with advanced HOT format arrays. The paper will also review planning for advanced Rotary version as further step of excellence with "SWAP-C" parameters.
The growing demand for EO applications that work around the clock 24hr/7days a week, such as in border surveillance systems, emphasizes the need for a highly reliable cryocooler having increased operational availability and optimized system's Integrated Logistic Support (ILS). In order to meet this need, RICOR developed linear and rotary cryocoolers which achieved successfully this goal. Cryocoolers MTTF was analyzed by theoretical reliability evaluation methods, demonstrated by normal and accelerated life tests at Cryocooler level and finally verified by field data analysis derived from Cryocoolers operating at system level. The following paper reviews theoretical reliability analysis methods together with analyzing reliability test results derived from standard and accelerated life demonstration tests performed at Ricor's advanced reliability laboratory. As a summary for the work process, reliability verification data will be presented as a feedback from fielded systems.
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.
Ricor cryogenics was founded in 1967 and since then it has focused on innovative technologies in the cryogenic field. The paper reviews the initial research and development efforts invested in various technologies that have yielded products such as Cryostats for Mossbauer Effect measurement, Liquid gas Dewar containers, Liquid helium vacuum transfer tubes, Cryosurgery and other innovative products. The major registered patents that matured to products such as a magnetic vacuum valve operator, pumped out safety valve and other innovations are reviewed here. As a result of continuous R and D investment, over the years a new generation of innovative Stirling cryogenic products has developed. This development began with massive split slip-on coolers and has progressed as far as miniature IDDCA coolers mainly for IR applications. The accumulated experience in Stirling technology is used also as a platform for developing self-contained water vapor pumps known as MicroStar and NanoStar. These products are also used in collaboration with a research institute in the field of High Temperature Superconductors. The continuous growth in the cryogenic products range and the need to meet market demands have motivated the expansion, of Ricor's manufacturing facility enabling it to become a world leader in the cryocooler field. To date Ricor has manufactured more than 120,000 cryocoolers. The actual cryogenic development efforts and challenges are also reviewed, mainly in the field of long life cryocoolers, ruggedized products, miniaturization and products for space applications.
KEYWORDS: Cryocoolers, Reliability, Cryogenics, Sensors, Accelerated life testing, Systems modeling, Interfaces, 3D modeling, Chemical analysis, Algorithm development
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
more.
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 world growth in research and development of High Operating Temperature (HOT) IR detectors impels the
development and optimization of suitable cryocoolers. The current developments at RICOR, which include three
different cryocooler models and two new controllers, are focused on the - oriented design process, meaning small
Size, low Weight, low Power consumption, improved performance and lower production cost, providing proper
cryocoolers for future hand held thermal imagers.
This paper shows the progress made during development of “HOT” cryocooler prototypes, engineering pre-production
series and qualified production series cryocoolers working at the FPA temperature range of 130 - 200K. The progress
with development of electronic control modules providing minimized regulated power consumption is also shown.
The progress in development of cryocoolers reliability is also reported in the paper.
KEYWORDS: Cryogenics, Space operations, Sensors, Aerospace engineering, Mars, Temperature metrology, Fermium, Frequency modulation, Climatology, Helium
Cryogenic refrigerators represent a significant enabling technology for Earth and Space science enterprises. Many of the space instruments require cryogenic refrigeration to enable the use of advanced detectors to explore a wide range of phenomena from space. RICOR refrigerators involved in various space missions are overviewed in this paper, starting in 1994 with “Clementine” Moon mission, till the latest ExoMars mission launched in 2016. RICOR tactical rotary refrigerators have been incorporated in many space instruments, after passing qualification, life time, thermal management testing and flight acceptance. The tactical to space customization framework includes an extensive characterization and qualification test program to validate reliability, the design of thermal interfacing with a detector, vibration export control, efficient heat dissipation in a vacuum environment, robustness, mounting design, compliance with outgassing requirements and strict performance screening. Current RICOR development is focused on dedicated ultra-long-life, highly reliable, space cryogenic refrigerator based on a Pulse Tube design
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 growing demand for Electro Optic (EO) applications that work around the clock 24hr/7days a week, such as in border surveillance systems, emphasizes the need for a highly reliable Cryocooler having increased operational availability and decreased integrated system Life Cycle (ILS) cost. In order to meet this need, RICOR has developed Integral Rotary and Split Linear Cryocoolers technologies which meet this challenge. RICOR’s Cryocoolers reliability characteristics are assessed by analytical reliability models, demonstrated by normal and accelerated life tests and finally verified by field data. The paper will focus on the reliability evaluation models for different technologies, report and analyze life demonstration test data at different mission profiles and verify the results by fielded Cryocoolers operating as a feedback to approve the theoretical assumptions and calculation models. In addition, it will review the system's end user needs and expectations from advanced high reliable Cryocoolers.
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 world growth in research and development of High Operating Temperature IR detectors impels the development
process and the optimization of rotary crycoolers at RICOR.
The design aspects of size weight and power and the tradeoffs between them, were taken into consideration during the
development process in order to optimize IDDCA for future hand held thermal sights.
This paper will present optimization tests results performed for rotary crycoolers at the temperature range of 110 - 200K
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.
As a result of the new approach to Rotary crycoolers for HOT detectors, the improvement in the reliability is analyzed
and will be reported in the paper.
The growing demand for EO applications that work around the clock 24hr/7days a week, such as in border surveillance
systems, emphasizes the need for a highly reliable cryocooler having increased operational availability and decreased
integrated system Life Cycle (ILS) cost. In order to meet this need RICOR has developed a new rotary Stirling
cryocooler, model K508N, intended to double the K508's operating MTTF achieving 20,000 operating MTTF hours.
The K508N employs RICOR's latest mechanical design technologies such as optimized bearings and greases, bearings
preloading, advanced seals, laser welded cold finger and robust design structure with increased natural frequency
compared to the K508 model.
The cooler enhanced MTTF was demonstrated by a Validation and Verification (V&V) plan comprising analytical
means and a comparative accelerated life test between the standard K508 and the K508N models. Particularly, point
estimate and confidence interval for the MTTF improvement factor where calculated periodically during and after the
test. The (V&V) effort revealed that the K508N meets its MTTF design goal. The paper will focus on the technical and
engineering aspects of the new design. In addition it will discuss the market needs and expectations, investigate the
reliability data of the present reference K508 model; and report the accelerate life test data and the statistical analysis
methodology as well as its underlying assumptions and results.
The growth in world demand for infrared missile warning systems (MWS) has impelled the development of new
technologies, in particular, special cryogenic coolers. Since the cryocooler is a core component in MWS 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.
The development focused on a cryocooler regenerator and cold finger optimization in order to achieve high cooling
capacity and a thermodynamic efficiency of about 4.4% at 95°C ambient for one of the cooler models.
In order to withstand harsh environmental vibration, the cold finger and outer Dewar structure have been significantly
ruggedized; efficient heat sinking methods have been applied and also novel vibration isolation methods have been
implemented.
The electronic design concept is based on an analog controller, the PCB of which has been designed with internal heat
sinking paths and special components being able to withstand ambients temperatures up to 125°C.
As a final stage of development, such cryocoolers were successfully qualified by RICOR and system manufacture in
harsh environmental conditions and life demonstration tests were performed.
Novel compact and low power consuming cooled infrared thermal imagers as used in gyro-stabilized payloads of
miniature unmanned aerial vehicles, Thermal small arms sights and tactical night vision goggles often rely on integral
rotary micro-miniature closed cycle Stirling cryogenic engines.
Development of EPI Antimonides technology and optimization of MCT technology allowed decreasing in order of
magnitudes the level of dark current in infrared detectors thus enabling an increase in the optimal focal plane
temperature in excess of 95K while keeping the same radiometric performances as achieved at 77K using regular
technologies.
Maintaining focal plane temperature in the range of 95K to 110K instead of 77K improves the efficiency of Stirling
thermodynamic cycle thus enlarging cooling power and enabling the development of a mini micro cooler similar to
RICOR's K562S model which is three times smaller, lighter and more compact than a standard tactical cryocooler like
RICOR's K508 model.
This cooler also features a new type of ball bearings and internal components which were optimized to fit tight bulk
constraints and maintain the required life span, while keeping a low level of vibration and noise signature. Further, the
functions of management the brushless DC motor and temperature stabilization are delivered by the newly developed
high performance sensorless digital controller.
By reducing Dewar Detector thermal losses and increasing the focal plane temperature, longer life time operation is
expected as was proved with RICOR's K508 model.
Resulting from this development, the RICOR K562S model cryogenic engine consumes 1.2 - 3.0 WDC while operating
in the closed loop mode and maintaining the typical focal plane arrays at 200-100K. This makes it compatible with very
compact battery packages allowing further reduction of the overall thermal imager weight thus making it comparable
with the compatible uncooled infrared thermal imager relying on a microbolometer detector in terms of power
consumption and bulk.
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