Thermal measuring and testing – Determination of inherent thermal property
Reexamination Certificate
1999-06-11
2001-08-14
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Determination of inherent thermal property
C374S044000, C374S124000
Reexamination Certificate
active
06273603
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention refers to a measuring head for use in radiant energy flash measuring of the thermal diffusivity of heterogeneous samples, in particular of heterogeneous highly radioactive samples or other samples for which remote manipulation is required.
2. Description of the Related Art
From W. J. Parker, R. J. Jenkins, C. P. Butler and G. L. Abbot, J. Appl. Phys. 32(9), 1679-1684 (1961) the so-called “flash method” for measuring the thermal diffusivity “a” is known. In this method the front face of a small disc-shaped specimen or sample is subjected to a very short burst of radiant energy coming from a laser or a flash lamp. The method employs irradiation times in the order of one millisecond. The resulting temperature rise of the rear surface of the sample is measured and recorded, and then thermal diffusivity values are computed from temperature rise versus time.
The simplest and most frequently used way to calculate thermal diffusivity is to use t
½
as a characteristic time, i.e. the time needed for the rear side temperature to reach 50% of its maximum value:
a=
0.1388L
2
/t
½
(m
2
/s)
From R. E. Taylor and K. D. Maglic, in: Compendium of Thermophysical Property Measurement Methods 2 (K. D. Maglic, A. Cezairliyan and V. E. Peletsky, eds.) 281-314, Plenum Press, New York (1991) a method for carrying out a transient temperatur measurement is known. The detector for measuring the transient temperature may be a thermocouple, a infrared detector or an optical pyrometer. The detector must be capable to record 0.1 degree change above the ambient temperature. The response time of the detector/amplifier combination must be less than 10% of t
½
.
FIG. 4
illustrates schematically the known method for measuring the thermal diffusivity.
The prior art measuring heads for carrying out the above described method for measuring the thermal diffusivity are used in connection with lasers as a radiant energy generating means and a detector means for detecting a temperature rise at the rear side of the sample. They comprise a sample holder means for receiving the sample to be measured. However, they are all constructed in view of producing and analysing a pre-fixed type of temperature spike. They in particular do not offer the opportunity to align the sample with the probe beam generated by the laser. Thus the energy shot cannot be deposited on the most suitable area, dependently on the given sample features, and a local axial diffusion measurement cannot be performed.
SUMMARY OF THE INVENTION
Therefore, it is the object of the present invention to provide a measuring head for use in radiant energy flash measuring of the thermal diffusivity of heterogeneous samples by means of which local measurements of the thermal diffusivity can be carried out without substituting the sample holder.
According to the present invention it is proposed to provide a measuring head for use in radiant energy flash measuring of the thermal diffusivity of heterogeneous samples under employment of a probe beam generated by a radiant energy generating means and a detector means for detecting a temperature rise of the sample, comprising a sample holder means for receiving the sample with a sample holder means which is movable in at least one direction perpendicular to the optical axis of the probe beam. Preferably, a laser is used as a radiant energy generating means but a flash lamp or other suitable means for generating a probe beam can be employed.
The measuring head according to the present invention offers the advantage that the sample can be easily aligned with the probe beam generated by the radiant energy generating means in order to carry out local measurements of the thermal diffusivity and to deposit the energy shot on the most suitable area of the sample, dependently on the given sample features.
According to further features of the present invention the measuring head has an adjustable viewing head for shifting a detector probe spot from a first position on the sample to a second position on the sample.
Thus, it is made possible to change the measurement method from axial diffusion measurement to radial diffusion measurement without substituting the sample holder. The viewing head optics comprising substantially a mirror having a field stop hole determining the field of the sample to be measured can be adjusted and thereby focused on an arbitrary zone of the sample surface independently of the position and size of the probe beam spot. Therefore, in non-homogeneous samples the diffusivity can be measured in different positions by using the radial analytical method without moving the sample and disturbing the background temperature provided by a furnace means surrounding the sample. Finally, thanks to the mirror of the viewing head optics, on which the field stop aperture is located, a full image of the sample is obtained, enabling the coordinates of the measured area to be accurately determined.
Thus, the present invention provides a multipurpose measuring head for measuring the thermal diffusivity.
Since in particular highly radioactive samples are to be measured it is important to keep all delicate parts involved like the radiant energy generating means, the detector and the preamplifiers at an arbitrary distance from the sample. This is achieved by employing optical fibers for transmitting the light emitted by the sample and seen by the field stop hole to the detector and for transmitting the radiant energy from the radiant energy generating means to a radiant energy input means delivering the probe beam into a lead-shielded cell containing the furnace means, an objective, the mirror and the sample holder means.
The radiant energy input means being movable in at least one direction perpendicular to the optical axis of the probe beam offers the advantage that the probe beam spot can be focused on areas of arbitrary sizes, making it possible to create the optimal temperature-spike conditions for the envisaged measurement method. Said radiant energy input means is arranged on one side of the sample holder while said adjustable viewing head is arranged on the opposite side of the sample holder. In other words, said probe beam is directed to one side of the sample while said adjustable viewing head is directing a detector probe spot on an arbitrary zone on the opposite side of the sample.
The adjustable viewing head additionally has a telescope for monitoring the shifting movement of the detector probe spot and the objective is arranged for focussing the light emitted by the sample to the viewing head.
The sample holder means is detachably fixed to the furnace means surrounding the sample. Thus, the furnace means is movable together with the sample holder means. Preferably, the furnace means consists of at least one high frequency (HF) coil and thermic shields which facilitates a movement of the furnace means and the sample holder means even when the measuring head according to the present invention is in operation.
REFERENCES:
patent: Re. 28954 (1976-09-01), Baker et al.
patent: 3427861 (1969-02-01), Maley
patent: 3501380 (1970-03-01), Perch
patent: 3803413 (1974-04-01), Vanzetti et al.
patent: 3892125 (1975-07-01), Nunogaki
patent: 4243327 (1981-01-01), Frosch et al.
patent: 4557607 (1985-12-01), Busse
patent: 4591272 (1986-05-01), Morris et al.
patent: 4594510 (1986-06-01), Brown et al.
patent: 4853541 (1989-08-01), Duhrkoop
patent: 4874251 (1989-10-01), Thomas et al.
patent: 5085073 (1992-02-01), Heyman et al.
patent: 5478151 (1995-12-01), Duhrkoop
patent: 5667300 (1997-09-01), Mandelis et al.
patent: 5688049 (1997-11-01), Govorkov
patent: 5760400 (1998-06-01), Prekel et al.
patent: 5923036 (1999-07-01), Tague, Jr. et al.
patent: 6062729 (2000-05-01), Ni et al.
patent: 6074087 (2000-06-01), Chen et al.
patent: 355065142A (1980-05-01), None
Section E1, Week 9333, Oct. 6, 1993, Derwent Publications ltd., London, GB; Class S03, p. 5 AN 93-263630, Gorinskii, S.G. “Determination of Temperature Conductivity of Materia
Cheindline Mikhail
Ronchi Claudio
Euratom
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Gonzalez Madeline
Gutierrez Diego
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