What is Cryogenic Design?

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Sapphire for Cryogenic Design

Development of ultra-stable cryogenic sapphire oscillators (CSOs) with low-vibration cryocoolers and custom cryostats has delivered unprecedented performance [2] [4] in a low-maintenance package accompanied by the need to generate user frequency (RF) and millimeter (X-band) signals with low degradation of signal quality. The cryogenic Sapphire Oscillator (CSO) is a stable source of microwave signals with a short integration time that provides stability in parts of 10-16 1 / s and 5x103 / s and no drifting 5x10-15 1 / day. Sapphire crystals are an ultra-stable frequency reference that shows no significant drift after a day of integration. [Sources: 5, 8]

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Cryogenic Design Research

This research examined the effects of thermal circulation in a room at cryogenic temperatures between 300K and 4K on thermal expansion coefficients of two ceramic substrates: silicon nitride (Si3N4) and alpha alumina (sapphire) (Al2O3). We also reported on the reduction of thermal lenses in cryogenic sapphire mirror planes using the large-scale cryogenic gravity wave telescope project (LCGT). [Sources: 0, 2]

We measure three key parameters of the sapphire substrate: thermal lens and cryogenic temperature. These parameters are the optical absorption coefficient, the thermal conductivity, the temperature coefficient and the refractive index at cryogenic temperatures. [Sources: 0]

Based on these measurements, we estimated the shot sensitivity of interferometer thermal lenses using wavefront simulations. White CSI samples were used and optical absorption measurements were performed. [Sources: 0]

The signal degradation at 100 MHz was estimated at less than 10 MHz due to the self-noise in the frequency divider component used. The performance of T = 10.3 s was superior to previous results. One of the frozen sapphire oscillators was built with the same spiral crystal four times after the measurements, but one of the thermal stabilization features with passive thermal filtering was not implemented. [Sources: 8]

Chapter 4 examines the influence of crystal orientation on the tensile strength of hydroxide catalysis bonds in sapphire. In this paper we report on the results of two samples of sapphire obtained from boules grown using a modified Kyropoulos method by melting raw material in a crucible and putting the seeds in contact with a bath in which the temperature is lowered to control the way the crystals grow in the bath. [Sources: 6, 9]

The focused beam is modulated by the optical chopper with a fixed frequency and the temperature changes are modulated linearly. The power absorbed by our sample is low and the amplitude of temperature modulation is proportional to its local absorption coefficient. It should be noted that the absorption coefficient contains secondary contributions, such as thermal loads mediated by changes in the refractive index. [Sources: 9]

Knowledge of fluorescence cross sections and line shapes at cryogenic temperatures is of crucial importance to the designer of CPA laser systems to model the amplification process and performance of the laser system. [Sources: 1]

Section 2 describes measurements of the fluorescence spectrum at temperatures from 77K to 300K. Section 3 presents calculations of the amplification cross-section and the line shape as well as corresponding fit parameters, which are used for modelling the CPA gain. Section 4 presents simulations of multipass amplifiers with the amplification and line shapes presented in Section 3 at cryogenic and room temperatures. [Sources: 1]

The two most promising candidates for cryogenic mirrors with suspension elements are sapphire and silicon. A cryogenic detector, the Japan-based Karag Observatory, is under construction and uses sapphires as material for its mirror suspension elements. [Sources: 6]

One such area of further development is the pair operation of detectors at cryogenic temperatures where improvements in mirror and suspension design are aimed at increasing sensitivity and reducing thermal noise effects. Due to its unfavourable thermomechanical properties, quartz glass used as a mirror surface, suspension fiber and elements for detectors at room temperature can't be used in cryogenic temperature detectors. Changes in mirrors, substrates and suspension materials are therefore necessary for the construction of cryogenic detectors. [Sources: 6]

This paper examines the latest developments in high-performance gyrotronoscillators for fusion plasma and industrial applications. The purpose of this section is to show that significant changes in the amplified laser spectra can be used for cryogenic cooling. Gyrotron oscillators can also be used for material processing. [Sources: 1, 4]

For the 100-TW laser system used in this case study [8,27] there are two multi-pass amplifier stages based simulations on a 3D amplification model [27]. With the Jaeri FZK-GYCOM an overall efficiency of 50-60% was achieved using a single-stage depressive collector (SDC). [Sources: 1, 4]

The additional surveillance power is particularly important in the defence context and provides additional intelligence. Sapphire watches are the culmination of 20 years of cutting-edge research that has shown the world how to beat laboratory performance. In response to the call for better radar signals, the Sapphire team began working with the High Frequency Radar Team (DST) to research the JORN project. [Sources: 3]

 

##### Sources #####

[0]: https://www.arxiv-vanity.com/papers/gr-qc/0202038/

[1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5772427/

[2]: https://asmedigitalcollection.asme.org/InterPACK/proceedings/InterPACK2019/59322/V001T06A022/1071535

[3]: https://www.adelaide.edu.au/ipas/our-research/defence-security/cryogenic-sapphire-oscillator-the-sapphire-clock

[4]: https://www.osti.gov/servlets/purl/5564357

[5]: https://teams.femto-st.fr/equipe-ohms/cryogenic-sapphire-oscillators

[6]: http://theses.gla.ac.uk/30604/

[7]: https://pubmed.ncbi.nlm.nih.gov/20442014/

[8]: https://onlinelibrary.wiley.com/doi/10.1049/el.2013.3481

[9]: https://www.nature.com/articles/s41598-020-80313-1