LDR cryogenics

A brief summary from the 1985 Large Deployable Reflector (LDR) Asilomar 2 workshop of the requirements for LDR cryogenic cooling is presented. The heat rates are simply the sum of the individual heat rates from the instruments. Consideration of duty cycle will have a dramatic effect on cooling requirements. There are many possible combinations of cooling techniques for each of the three temperatures zones. It is clear that much further system study is needed to determine what type of cooling system is required (He-2, hybrid or mechanical) and what size and power is required. As the instruments, along with their duty cycles and heat rates, become better defined it will be possible to better determine the optimum cooling systems

Cryogenics for LDR

Three cryogenic questions of importance to Large Deployable Reflector (LDR) are discussed: the primary cooling requirement, the secondary cooling requirement, and the instrument changeout requirement

An Introduction to Cryogenics

This paper aims at introducing cryogenics to non-specialists. It is not a cryogenics course, for which there exists several excellent textbooks mentioned in the bibliography. Rather, it tries to convey in a synthetic form the essential features of cryogenic engineering and to raise awareness on key design and construction issues of cryogenic devices and systems. The presentation of basic processes, implementation techniques and typical values for physical and engineering parameters is illustrated by applications to helium cryogenics

Improved liquid-level sensor for cryogenics

Liquid-level indicator, consisting of a diode heated by a resistor, allows simultaneous use of two or three of the liquids nitrogen, hydrogen, and helium. Operation depends on strong temperature-dependence of the forward resistance of a germanium diode and the difference between liquid and vapor in heat-transfer properties

NTF: Soldering Technology Development for Cryogenics

The advent of the National Transonic Facility (NTF) brought about a new application for an old joining method, soldering. Soldering for use at cryogenic temperatures requires that solders remain ductile and free from tin-pest (grey tin), have toughness to withstand aerodynamic loads associated with flight research, and maintain their surface finishes. Solders are used to attach 347 Stainless-Steel tubing in surface grooves of models. The solder must fill up the gap and metallurgically bound to the tubing and model. Cryogenic temperatures require that only specific materials for models can be used, including: Vasco Max 200 CVM, lescalloy A-286 Vac Arc, pH 13-8 Mo. Solders identified for testing at this time are: 50% Sn - 49.5% Pb - 0.5% Sb, 95% Sn - 5% Sb, 50% In 50% Pb, and 37.5% Sn - 37.5% Pb - 25% In. With these materials and solders, it is necessary to determine their solderability. After solderability is determined, tube/groove specimens are fabricated and stressed under cryogenic temperatures. Compatible solders are then used for acutual models

Path-finding towards a cryogenic interferometer for LIGO

LIGO is exploring cryogenics as a technique of last resort to reduce the thermal noise of mirrors and suspensions in gravitational wave interferometric detectors. Some of the cryogenic, or cryogenic-related, R&D done at LIGO is reported here. Some ideas being considered to make cryogenics possible may be useful even for room temperature detectors