U.S. patent application number 11/572836 was filed with the patent office on 2008-04-24 for cryogenic cooling device.
This patent application is currently assigned to Target Systemelectronic GmbH. Invention is credited to Guntram Pausch, Jurgen Stein.
Application Number | 20080092556 11/572836 |
Document ID | / |
Family ID | 35134058 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080092556 |
Kind Code |
A1 |
Stein; Jurgen ; et
al. |
April 24, 2008 |
Cryogenic Cooling Device
Abstract
The present invention relates to a cryo temperature cooling
device (1)comprising 5 a tank (2), being filled up at least in part
with a coolant (3), and a heat conducting element (4), whereas the
heat conducting element (4) can be brought into thermal contact
with the coolant (3), so that the coolant has a phase transition
occurring below a temperature of -100.degree. C., so that the
cryogenic cooling device more or less consumes no coolant during
operation.
Inventors: |
Stein; Jurgen; (Wuppertal,
DE) ; Pausch; Guntram; (Dresden, DE) |
Correspondence
Address: |
IP STRATEGIES
12 1/2 WALL STREET, SUITE I
ASHEVILLE
NC
28801
US
|
Assignee: |
Target Systemelectronic
GmbH
Solingen
DE
|
Family ID: |
35134058 |
Appl. No.: |
11/572836 |
Filed: |
July 28, 2005 |
PCT Filed: |
July 28, 2005 |
PCT NO: |
PCT/EP05/53707 |
371 Date: |
November 5, 2007 |
Current U.S.
Class: |
62/45.1 ;
62/529 |
Current CPC
Class: |
F25D 2303/085 20130101;
F25D 19/006 20130101; F25D 3/00 20130101 |
Class at
Publication: |
62/45.1 ;
62/529 |
International
Class: |
F25D 3/10 20060101
F25D003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 28, 2004 |
DE |
10 2004 036 483.4 |
Sep 10, 2004 |
DE |
10 2004 043 900.1 |
Claims
1. Cryo temperature cooling device comprising a tank, being filled
up at least in part with a coolant, and a heat conducting element,
whereas the heat conducting element can be brought into thermal
contact with the coolant, characterized in that the coolant has a
phase transition occurring below a temperature of -100.degree. C.,
so that the cryogenic cooling device more or less consumes no
coolant during operation.
2-25. (canceled)
26. Measurement device, comprising a detector and a cryo
temperature cooling device according to claim 1 for cooling the
detector, comprising at least one of the following features: the
measurement device is set up as a portable handheld device, the
measurement device is set up as a spectrometer, the detector
comprises a semiconductor detector, preferably using germanium, for
the measurement of ionizing radiation, at least one cooling finger
of the cryo temperature cooling device is in thermal contact to the
detector.
27-41. (canceled)
42. Cooling device for the cooling down of a cryo temperature
cooling device according to claim 1, characterized in that the
cooling device for the cooling down of the cryo temperature cooling
device can be connected thermally with said cryo temperature
cooling device and where the cooling down is provided mainly via
said thermal connection and mainly without material exchange
between cooling device and the cryo temperature cooling device to
be cooled down.
43. (canceled)
44. (canceled)
Description
[0001] The invention refers to a cryogenic cooling device, a
device, comprising a component to be cooled, which is cooled by a
cryogenic cooling device, as well as to a cooling element for the
cooling of the cryogenic cooling device.
[0002] From the prior art, a multitude of cooling devices are
known, being used in order to cool down, for example, sensors,
electric circuits or detectors and others. The cooling of radiation
detectors is of specific importance, as the measured spectra are
imprecise if there is no appropriate cooling, as especially the
energy and time resolution of the measured values are strongly
dependent from the temperature. Just among radiation detectors,
using semiconductor crystals, for example germanium, a good cooling
of mostly below -100.degree. C. is of essential importance.
[0003] It is known in addition that different cooling temperatures
are necessary for different detectors. Germanium or silicon
detectors for the detection of x-ray or gamma-radiation for example
do need a cooling to about 95 K to 130 K in order to achieve
sufficiently good measurement results.
[0004] In order to achieve such cooling temperatures, especially in
order to achieve a cooling down to a cryogenic temperature, that is
below -100.degree. C., the prior art is using liquid nitrogen,
helium or other liquefied gas. It is also known to use a stirling
cooling, a Peltier transition, the Joule-Thomson-effect or others.
Those known cooling systems do, nevertheless, need large space, are
heavy and therefore not or only very limited suitable for the
cooling of handheld devices.
[0005] Comparably large and heavy, but, nevertheless, portable
radiation detectors for the measurement of gamma radiation are,
according to the prior art, cooled mechanically, whereby
accumulator cells, for example NiCd accumulators, are used for the
operation of the cooling devices.
[0006] From UCRL-JC-118973 and UCRL-JC-119679, an electro
mechanical cooling mechanism is known, used for a portable
germanium detector. As with all mechanical cooling devices, the
cooling device described here has the disadvantage that mechanical
vibrations affect the quality of the measurement. The detector
system with the cooling device has a power consumption of 37 to 97
Watt, therefore requiring big and heavy batteries. The complete
system described, consisting of detector, cryo cooler and battery,
weights 18.2 kg, therefore being not well suited for the mobile use
in the field already because of its weight and its size.
[0007] In IEEE Transactions on Nuclear Science, Vol. 40, No. 4,
August 2003, page 1043-1047, a portable germanium detector is
described, which is cooled by the use of a stirling cooler on the
basis of electricity also. The cooling described therein also leads
to a reduced resolution because of vibrations. In addition, the
necessary cooling power could be upheld for two hours only by using
6 AH NiMH accumulators.
[0008] All mentioned cooling systems, receiving the energy from
battery powered power sources, do not provide enough power in order
to cool down a semiconductor crystal to its operating temperature
sufficiently fast. Only when the cooling occurs fast enough, the
cryo pump, being part of the detector, comprising regularly
activated charcoal, is activated, thereby improving the vacuum
inside the detector. When the cooling process is slow, no
activation occurs, which again leads, because of the additional
impurities remaining in the crystal, to a deterioration of the
resolution.
[0009] Known cooling systems in the form of cooling accumulators,
which do not show those disadvantages and which would be suitable
for portable use, for example cooling accumulators for the cooling
of beverages or for the treatment of swellings, which for example
make use of eutectic cooling, cannot provide a cryo temperature,
being necessary for the operation of the semiconductor detectors.
Nevertheless, only when using cooled semiconductor crystals, energy
resolutions better than 1% at 662 keV can be achieved.
[0010] Portable radiation detectors, which could be easily used
mobile, especially for the measurement of gamma radiation, do
therefore make use only of crystals and materials, which may be
practically used in the respective surrounding temperature field,
that is preferably in a temperature area between -25.degree. C. to
+50.degree. C., offering a sufficient resolution in that
temperature area. Regularly, NaI or CsI crystals are used here, but
also plastic scintillators as well as so called room temperature
semiconductor crystals (CdZnTe), which, nevertheless, by far do not
achieve the measurement accuracy, which can be achieved with cooled
semiconductor crystal detectors.
[0011] The problem underlying the present invention is therefore to
provide a cryo temperature cooling device, being suitable for the
cryo cooling of portable devices, avoiding the described
disadvantages. This problem is, according to the invention, solved
by a cryo temperature cooling device with the features according to
claim 1. Preferred embodiments of the cryo temperature cooling
device as described in the invention are provided in the dependent
claims.
[0012] The cryo temperature cooling device according to the
invention comprises a holding tank, being filled up at least in
part with a coolant, and a heat conducting element, whereas the
heat conducting element is in thermal contact with the coolant. The
coolant serves as a heat sink during operation, that is in other
words as a "cooling accumulator". It can take particularly more
heat, if there is a phase change within the temperature area of
interest, preferably providing a high phase transition energy,
which is when looking at a phase transition solid-liquid, a
preferably high latent heat of fusion. Nevertheless, a coolant
without a phase transition in the temperature area of interest is
also providing good results, as long as the cooling device is
sufficiently insulated.
[0013] According to the invention, the coolant preferably provides
for a phase transition from the group solid-solid, solid-fluid, and
fluid-fluid, occurring below a temperature of -100.degree. C., so
that the cryogenic cooling device more or less uses or consumes no
coolant during operation, as the volumes of the various phases can
be kept constant, being the reason that mainly no coolant has to be
sent to the surrounding, that is to be consumed. The constant
volumes are achieved by either providing a sufficiently solid
pressure tank, being pressure resistant and able to surround the
coolant in the complete area of temperatures during operation of up
to about 55.degree. C., and/or by selecting suitable coolants,
their vapor pressure being low in the complete temperature field
during operation, preferably not being larger than the surrounding
air pressure.
[0014] According to a preferred embodiment, the coolant comprises
an organic compound, comprising a heat of fusion of less than
-100.degree. C. Said coolant preferably comprises one or more of
the following compounds: vinyl bromide (brome ethylene), ethyl
bromide (brome ethane), butane, butene-2-cis, ethyl acetylene,
butene-1 and isobutene. The suitable compounds are known in
principle and can be found in respective tables, for example from
the CRC Handbook of Chemistry and Physics.
[0015] Vinyl bromide (C.sub.2H.sub.3Br) is of especial advantage as
a coolant, as it has a melting point of -138.degree. C. (=135.2 K),
a heat of fusion of about 15.7.degree. C. as well as a vapor
pressure of 1.20 bar at room temperature (21.degree. C.). An
additional advantage is the high density of 1.5 kg/dm.sup.3 of
vinyl bromide. Therefore, the volume of the coolant, necessary for
a sufficient cooling, is reduced, thus reducing the volume of the
inventive device and at the same time increasing its
portability.
[0016] The energy radiation and therefore the thermal loss during
storage and operation of the inventive device is nearly
proportional to the difference of the 4.sup.th power of the coolant
temperature and the 4.sup.th power of the surrounding temperature
(Law of Stefan-Bolzmann). As the cooling temperature of
-138.degree. C. of vinyl bromide is sufficient for the cooling of
semiconductor detectors, especially of germanium detectors, the
energy loss by thermal radiation is much smaller compared to a
cooling with liquid nitrogen. This is increasing the effective
cooling time even with respect to conventional nitrogen cooling
substantially.
[0017] Using vinyl bromide as a coolant, the inventive cryo
temperature cooling device can be kept at a nearly constant
temperature of substantially lower than -100.degree. C., more
specifically of -138.degree. C., for a time period of at least
eight hours with 0.5 to 1.0 liter of coolant only. At the same
time, the cooling temperature is reached fast enough in order to
activate a cryo pump within a germanium detector, comprising
activated charcoal on a regular basis, serving for improving the
vacuum within the detector crystal.
[0018] The cryo temperature cooling device may also use butane,
butene-2-cis, ethyl acetylene, butene-1, isobutene or ethyl bromide
as a coolant, as those substances do show similar properties than
vinyl bromide. Also a mixture of various coolants may be used.
[0019] Preferably, the cryo temperature cooling device provides a
coolant with a phase transition temperature (T.sub.p) below
-140.degree. C., whereby it has proved a specific advantage, if the
coolant provides a boiling temperature T.sub.SI higher than
20.degree. C., preferably higher than 50.degree. C.
[0020] Furthermore, it has proved to be of advantage if the coolant
has a phase transition energy of at least 35 kJ/ltr, preferably a
phase transition energy of at least 50 kJ/ltr and especially
preferred of at least 80 kJ/ltr.
[0021] It furthermore is an advantage if the coolant is selected in
such a way that the vapor pressure of the coolant at room
temperature (21.degree. C.) is preferably below 3 bar, especially
preferable 1.5 bar, where the vapor pressure is not increasing
substantially at the maximum operation temperature. It is
especially an advantage if the vapor pressure of the coolant at
20.degree. C., preferably even at 50.degree. C., does not exceed a
value of 1 bar.
[0022] Especially during practical use it has been proven that it
is an advantage to select the coolant in such a way that the
product of the volume, being available for the coolant within the
tank, and the vapor pressure of the coolant at room temperature, is
lower than 30 bar ltr, preferably lower than 20 bar ltr and
especially preferable lower than 10 bar ltr.
[0023] This is especially of advantage with regard to the tank, as
this should be exposed preferably only to low strain in order to
provide for a long durability with regard to the cryo temperature
cooling device. In addition, when only providing limited stress to
the tank, cost effective materials could be used. Furthermore, the
safety requirements, especially in more sensitive areas, for
example in aviation, are much less strict when using tanks with a
low pressure only, which additionally increases the field of
operation of the device according to the invention. Finally,
materials with a lower mass are sufficient for the making of the
tank, when the maximum vapor pressure is low only, preferably being
only inessentially higher than the pressure of the surrounding.
This leads to lighter tanks, therefore lowering the complete weight
of the device according to the invention, thus further increasing
their portability.
[0024] It is an advantage, when the heat conducting element is
situated in the device and protruding to the outside, whereas the
device preferably comprises a recess, being suitable to house the
heat conducting element, whereas the recess is made in such a way
that it allows for a thermal contact between the heat conducting
element on one side and the coolant within the device on the other
side. Preferably, the heat conducting element of the cryo
temperature cooling device is formed as a cooling finger.
[0025] Preferably, the phase transition temperature T.sub.P of the
coolant matches roughly the temperature, to which an object should
be cooled by using the cryo temperature cooling device.
[0026] In order to further increase the thermal transfer between
the coolant and the heat conducting element within the device,
further substances are added to the coolant, increasing the heat
conductivity according to a further preferred embodiment of the
invention.
[0027] For a specific application it can be vice-versa necessary to
lower the heat conduction. In that case, substances are mixed to
the coolant, which lower the thermal transfer.
[0028] The tank of the cryo temperature cooling device preferably
comprises an inner wall and an outer wall, having a distance from
the inner wall. In order to provide a good isolation of the cryo
temperature cooling device between the inner wall and the outer
wall of the pressure resistant tank, an intermediate area is
provided, comprising, according to a preferred embodiment of the
invention, a vacuum and/or a heat isolating material, for example
styrofoam.
[0029] The cryo temperature cooling device preferably is set up as
a mainly closed cooling accumulator, which can be cooled again with
a cooling device, for example with a compression refrigerating
machine, preferably at least down to the temperature of the phase
transition.
[0030] Furthermore, the heat conducting element, which is designed
to be within the tank of the cryo temperature cooling device, is
preferably adapted in order to be connected thermally to an object
to be cooled, especially to a detector, preferably a semiconductor
detector for the measurement of ionizing radiation.
[0031] It is possible to combine the heat conducting element with
the tank in such a way, that it protrudes out of this tank at the
same time being in thermal contact to the coolant in the inside.
For example, the semiconductor detector to be cooled then is
connected to the heat conducting element, for example plugged to
it. Vice-versa, the heat conducting element can also be connected
to the detector, maybe even fixed to the detector. The tank then
preferably provides a recession, with which the heat conducting
element can be connected to, for example by plugging, the recess.
The recess then is made up in such a way that it allows for thermal
contact between the coolant and the heat conducting element.
Preferably, the heat conducting element is formed as a cooling
finger.
[0032] This adoption can be made in such a way at the same time so
that it can act as a fixation of the cryo temperature cooling
device to an object to be cooled, when the object to be cooled
provides a respective plug for the heat conducting element.
Thereby, the tank of the cryo temperature cooling device may
provide additional devices in order to fix the cryo temperature
cooling device to the object to be cooled. Preferably, the heat
conducting element itself is fixed to the tank also.
[0033] Furthermore, the cryo temperature cooling device preferably
comprises a protective cap, which is detachably fixed to that part
of the heat conducting element, especially the cooling finger,
protruding from the tank. It is made shape congruent to the cooling
finger, whereby the protective cap preferably comprises a thermal
isolating material. The protective cap preferably is plugged to
that part of the cooling finger, protruding from the pressure tank,
as long as the device according to the invention is not in
operation mode, that is used for cooling, for example as long as it
is not coupled to a detector in order to cool it. In order to
activate the cooling function, the protective cap is removed from
the cooling finger.
[0034] According to a further aspect of the present invention, a
device is provided, comprising an element to be cooled and a cryo
temperature cooling device. This cryo temperature cooling device
comprises a tank, being filled at least partly with coolant. It is
further comprising a heat conducting element, whereas the heat
conducting element can be brought into thermal contact with the
coolant.
[0035] Thereby the device preferably comprises the following
features: it is designed as handheld device, the element to be
cooled is brought to an intended temperature below -100.degree. C.,
preferably below -140.degree. C., the cooling is effected by the
cryo temperature cooling device, whereas the coolant is working as
a low temperature reservoir, respectively as a heat sink, the
coolant not being consumed or sent to the environment during
operation, but remaining mainly within the tank. The cryo
temperature cooling device is re-loadable with the help of a charge
station, which may be designed stationary or portable, by removing
sufficiently enough heat from the coolant so that the following
operation of the device is possible for a sufficient period of
time, preferably at least one hour, especially preferred at least
eight hours and even more preferred at least 24 hours.
[0036] Also provided is a measurement device, comprising a detector
and a cryo temperature cooling device according to the invention,
comprising at least one of the following features: the measurement
device is set up as a portable handheld device, the measurement
device is set up as a spectrometer, the detector comprises a
semiconductor detector, preferably using germanium, for the
measurement of ionizing radiation, and at least one cooling finger
of the cryo temperature cooling device is in thermal contact to the
detector.
[0037] Preferably, the coolant used within the device comprises at
least one phase transition from the group solid-solid, solid-fluid
and fluid-fluid, occurring below a temperature of -100.degree.
C.
[0038] It has been proven to be of further advantage, if the cryo
temperature cooling device is detachable from the device, so that
the reload of the cryo temperature cooling device can occur when
separated.
[0039] The element to be cooled within the device may be an
electronic element, whose essential characteristics depend from its
temperature when used correctly, especially its operational
ability, noise and amplification, mainly becoming worse with rising
temperature. The electronic device thereby may be a sensor or a
detector for the detection of radiation, especially electro
magnetic and/or ionizing radiation, for example microwaves,
infrared, visible or ultra violet light, or of x-ray or
gamma-rays.
[0040] The term electronic device as used here has to be
interpreted very broadly and especially includes all devices,
making use of electro magnetic effects in the widest sense, that is
especially also detectors and detector crystals, but also a
detector crystal together with at least the first part of the
signal amplifiers of said detector.
[0041] The detector described preferably comprises a semiconductor
crystal, preferably comprising germanium or silicon. In addition,
it is an advantage if the detector comprises evaluation electronics
so that the measured radiation can be identified mainly within the
detector, whereas the detector preferably is set-up portable as
multi-purpose handheld Radio isotope Identifier Device (RID). Such
RIDs preferably comply with the relevant norms of the International
Atomic Energy Organization in Vienna (IAEO), especially with the
classification "Technical/Functional Specification for Border
Radiation Monitoring Equipment" as it has been ratified within the
Coordinated Research Project "Improvement of Technical Measures to
Detect and Respond to Illicit Trafficking of Nuclear and other
Radioactive Materials", Research Coordination and Technical Meeting
(M2-RC-927), Dec. 1-5, 2003, IAEA Headquarters, Vienna.
[0042] A second cryo temperature cooling device may be provided,
allowing for a larger cooling capacity. Said second cooling device
may be used stationary, whereas the detector preferably is
connected to this second cryo temperature cooling device when it is
not used in mobile mission. It, therefore, suits especially for the
long-term cooling of the detector between various missions. Such a
pre-cooling has the advantage that the limited cooling capacity of
the cooling accumulator according to the invention must not be used
first for the cooling down to the operation temperature, so that
the mission time of the system is extended.
[0043] After the cryo temperature cooling device has been warmed up
or at least used part of the cooling capacity, it can be reloaded
in such a cooling device used as a charging device, that is it can
be cooled down to a temperature preferably below the phase
transition of the coolant. Instead of coupling the coolant to the
object to be cooled, for example the semiconductor detector, the
coolant within the, optional pressure-resistant, tank is coupled to
the cooling device, whereby the cooling device preferably is a
conventional cooling device, for example making use of electro
mechanical cooling, for example of a compression refrigerating
machine, or of liquid gases like nitrogen or helium.
[0044] The cryo temperature cooling device according to the
invention may comprise also a second thermal coupling. The cryo
temperature cooling device may therefore be connected with the
object to be cooled, for example a circuit or a detector, the one
side and on the other side with the cooling device or a cooling
device with a higher capacity. In such a way, the complete system
including the object to be cooled can be cooled down so that the
complete system may be used for operational purposes immediately,
at the same time allowing for the maximum cooling capacity at the
beginning of the mission.
[0045] Furthermore, a cooling device for the cooling of the above
described cryo temperature cooling device is claimed, whereby the
cooling device may be coupled thermally to the cryo temperature
cooling device and whereby the cooling mainly occurs via the
thermal connection and mainly without a mass exchange between the
cooling device and the cryo temperature cooling device to be
cooled. This includes a cooling by using a flow of gas and/or a
flow of liquids, as long as the coolant of the cryo temperature
cooling device mainly remains within the cryo temperature cooling
device. The cooling device itself may be cooled by using liquid
gases, preferably with liquid nitrogen and/or liquid helium and/or
by using electric and/or mechanical cooling devices, for example a
compression refrigerating machine.
[0046] According to the invention, a compound, showing a phase
transition temperature of below -100.degree. C., is used as a
coolant in the cryo temperature cooling device. The compound may
be, according to one aspect of this invention, an organic compound,
for example vinyl bromide, butane, butene-2-cis, ethyl acetylene,
butene-1, isobutene or ethyl bromide.
[0047] According to even another aspect of the invention, the
coolant has a vapor pressure at room temperature (21.degree. C.) of
preferably below 3 bar, especially preferred of lower than 1.5 bar,
whereas it is explicitly an advantage if the vapor pressure of the
coolant at 20.degree. C., especially preferred at 50.degree. C.,
does not exceed a value of 1 bar.
[0048] In the following, the invention is described by using a
specific embodiment in the light of the enclosed figures.
[0049] The figures show:
[0050] FIG. 1 a cross sectional view through the cryo temperature
cooling device according to the invention;
[0051] FIG. 2 a cross sectional view through the measurement device
according to the invention;
[0052] FIG. 3 a top view to a portable measurement device according
to the invention;
[0053] FIG. 4 a further embodiment with a cooling device integrated
in the detector; and
[0054] FIG. 5 an embodiment with separate radiator coil.
[0055] FIG. 1 is a cross sectional view through the cryo
temperature cooling device 1 according to the invention. The tank 2
is preferably made from pressure resistant material so that it can
withstand the vapor pressure of the coolant 3 both at room
temperature as well as at the maximum operation or storage
temperature of the cryo temperature cooling device. A tank 2 in
addition is made in such a way that it comprises an inner wall 5
and an outer wall 6, having a distance from the inner wall 5 via an
intermediate area 7. The intermediate area 7 is filled with heat
insulating layers so that tank 2 respectively the cryo temperature
cooling device 1 separates the coolant sufficiently from the
surrounding temperature and that it remains in the frozen state for
a long term of time.
[0056] Within the tank 2 the coolant 3 is provided. The substances,
coming into question as a coolant for the cryo temperature cooling
device 1, stand out by a low phase transition temperature, for
example a low melting temperature, being roughly the temperature to
which an object is to be cooled, a preferably high heat of fusion,
preferably high boiling temperature and a preferably low vapor
pressure at the maximum operation/storage temperature. Some of the
substances to be considered and their relevant properties are
listed in the following, not completed Table 1:
TABLE-US-00001 TABLE 1 Melting Boiling Point Heat of Temperature
T.sub.S Fusion T.sub.SI Coolant Formula [.degree. C.] [kJ/l]
[.degree. C.] Pentaborane (11) B5--H11 -122.0 65.0 Phosphorotioc
bromide difluoride PSBrF2 -136.9 35.5 Trichlorosilane SiHCl3 -128.2
33.0 Sulfur dichloride SCl2 -122.0 59.6
1,2,2-Trichloro-1,1-difluoroethane C2--H--Cl3--F2 -140.0 71.9
1,2,2-Trichloro-1,2-difluoroethane C2--H--Cl3--F2 -174.0 72.5
1,1-Dichloroethene C2--H2--Cl2 -122.6 81.5 31.6 Bromoethene,
Bromoethylene, C2--H3--Br -139.5 71.8 15.8 Vinyl bromide
Acetaldehyde C2--H4--O -123.4 41.1 20.1 Ethyl bromide, Bromo ethane
C2--H5--Br -118.7 54.1 38.4 Ethane thiol C2--H6--S -147.9 66.7 35.1
1-Chloropropane C3--H7--Cl -122.9 62.8 46.5 1-Propanol C3--H8--O
-124.4 71.5 97.2 2-Propanethiol C3--H8--S -130.5 61.4 52.6 Butane
C4--H10 -138.0 81.2 -0.5 Butene-2 cis C4--H8 -139.0 130.2 3.7 Ethyl
acetylene C4--H6 -125.7 111.5 8.1 Butene-1 C4--H8 -185.4 68.6 -6.3
Isobutene C4--H8 -140.0 105.7 -6.9 cis-1,3-Pentadiene C5--H8 -140.8
57.2 44.1 1,4-Pentadiene C5--H8 -148.2 59.4 26.0
2-Methyl-1,3-butadiene C5--H8 -145.9 49.2 34.0 Cyclopentene C5--H8
-135.0 38.1 44.2 1-Pentene C5--H10 -165.1 54.3 30.0 cis-2-Pentene
C5--H10 -151.4 66.5 36.9 trans-2-Pentene C5--H10 -140.2 76.6 36.3
2-Methyl-1-butene C5--H10 -137.5 73.4 31.2 3-Methyl-1-butene
C5--H10 -168.4 47.5 20.1 2-Methyl-2-butene C5--H10 -133.7 71.8 38.6
trans-1,2-Dimethylcyclopropane C5--H10 -149.6 28.2
Ethylcyclopropane C5--H10 -149.2 35.9 Methylcyclobutane C5--H10
-161.5 36.3 Pentane C5--H12 -129.7 72.9 36.1 Isopentane C5--H12
-159.8 44.3 27.9 2-Pentanethiol C5--H12--S -169.0 112.9
Diethylmethylamine C5--H13--N -196.0 66.0 4-Methylcyclopentene
C6--H10 -160.8 65.7 1,5-Hexadiene C6--H10 -140.7 59.4 1-Hexene
C6--H12 -139.8 74.3 63.5 cis-2-Hexene C6--H12 -141.1 72.0 68.8
Methylcyclopentane C6--H12 -142.4 61.7 71.8 2,3-Dimethyl-1-butene
C6--H12 -157.3 55.6 Ethylcyclobutane C6--H12 -142.9 70.8
cis-2-Hexene C6--H12 -141.1 68.8 3-Methyl-1-pentene C6--H12 -153.0
54.2 4-Methyl-1-pentene C6--H12 -153.6 53.9
4-Methyl-trans-2-pentene C6--H12 -140.8 58.6 2-Methylpentane
C6--H14 -153.6 47.3 60.3 3-Methylpentane C6--H14 -162.9 40.6 63.3
2,3-Dimethylbutane C6--H14 -128.1 6.1 57.9 2-Hexanethiol C6--H14--S
-147.0 142.0 Triethylsilane C6--H16--Si -159.0 109.0 1-Heptene
C7--H14 -118.9 88.1 93.6 Methylcyclohexane C7--H14 -126.6 52.9
100.9 4-Methy-1-hexene C7--H14 -141.5 86.7 trans-2-Methyl3-hexene
C7--H14 -141.6 85.9 2,2-Dimethylpentane C7--H16 -123.7 39.1 79.2
3,3-Dimethylpentane C7--H16 -134.4 47.4 86.1
1-Ethyl-1-methylcyclopentane C8--H16 -143.8 121.6 3-Methylheptane
C8--H18 -120.5 71.8 118.9 4-Methylheptane C8--H18 -121.0 66.6
117.7
[0057] It is to be understood that Table 1 does not list all
coolants to be used according to the invention, but only a
selection. Especially, this selection is mainly limited to
substances with a boiling temperature T.sub.SI>20.degree. C. and
a melting temperature T.sub.S<-120.degree. C. Only butane,
butene-2 cis, ethyl acetylene, butene-1 and isobutene have been
mentioned in addition, even if their boiling temperature T.sub.SI
is lower than 20.degree. C. Suitable as coolants are propane and
propene also, but they do have a vapor pressure of 8.7 and 10.3 bar
at 21.degree. C., therefore requiring higher standards with regard
to the pressure resistance of the tank 2.
[0058] As a comparison, liquid nitrogen has a boiling temperature
of -196.degree. C. and a heat of fusion of about 161 kJ/ltr.
Suitable as coolants are also substances like propane and propene,
which nevertheless do have a vapor pressure of already 8.7
respectively 10.3 bar at 21.degree. C. and therefore having to meet
higher demands when it comes to the pressure stability of the
tank.
[0059] Furthermore, a heat conducting element 4 in the form of a
cooling finger, protruding from tank 2 through an opening 14
through the inner wall 5 and the outer wall 6, is seen in the cryo
temperature cooling device 1. The cooling finger 4 is surrounded
nearly completely from the coolant 3 within the tank 5. Mounted to
the part of the cooling finger 4, protruding from the cryo
temperature cooling device 1, is heat insulating protective cap 8.
So, the complete cryo temperature cooling device 1 is isolated from
the surrounding temperature as long as it is not in operation
respectively not used for the cooling of an object, therefore,
being able to be stored. The cooling finger 4 preferably also
comprises material, providing for a good heat transfer and at the
same time for the thermal connection between coolant and the object
to be cooled. It may for example be made from copper. In order to
further improve the heat transfer of the coolant 3 to the cooling
finger, further substances could be added to the coolant 3 in order
to promote this property.
[0060] The cryo temperature cooling device is used as follows: the
cryo temperature cooling device 1 is charged by bringing the
cooling finger 4 to a temperature below the melting point of the
coolant. When using vinyl-bromide, this would, for example, be a
temperature below -138.degree. C. (135.2 K). This cooling process
continues until the coolant is mainly frozen. The cooling,
respectively the charging of the cryo temperature cooling device 1,
is conducted with a charging device, for example a compression
refrigerating machine or with liquid nitrogen.
[0061] Afterwards, in order to store the cryo temperature cooling
device 1 until it is used for operational purposes, the protecting
cap 8 is mounted to the cooling finger 4. Therefore, a good heat
insulation of the cryo temperature cooling device 1 with regard to
the outside is achieved and the frozen state of the coolant 3 can
be kept fairly long.
[0062] When the cryo temperature cooling device 1 should be used
for cooling purposes, for example of a detector, the protective cap
8 is removed from the cooling finger 4 and the cooling finger 4 is
connected to the object to be cooled or included therein.
[0063] FIG. 2 shows a cross section at view of a cryo temperature
cooling device 1 according to the invention, which might be coupled
to a detector 10, comprising a detector support 15, a detector
crystal 16, being connected to a preamplifier, also mounted on the
detector support 15 and therefore cooled also, as well as an outer
wall 20. The outer wall in the embodiment is comprising a window,
being mainly transparent for the radiation to be measured, namely a
radiation entry window 21.
[0064] The cooling finger 4 of the detector 10 is thermally mounted
to the detector support 15, supporting also the detector crystal
16, for example a germanium crystal. There are, nevertheless, other
detector crystals suitable in order to be cooled by the inventive
cryo temperature cooling device 1, for example silicon crystal
detectors, CdTe-detectors and others. Preferably, the preamplifier
is thermally connected to the detector support 15 also so that this
is cooled, too. When the measurement respectively the operation
time of the detector 10 has ended, the cryo temperature cooling
device 1 can be removed from the detector 10 again in order to be
recharged for a further measurement.
[0065] As the size of the cryo temperature cooling device 1 is
small, it is especially suitable for the operation in combination
with a measurement device in the form of a handheld device 11,
which is shown schematically in a top view in FIG. 3.
[0066] Because of its low weight and volume this handheld device 11
is especially suitable for mobile missions, for example as gamma
ray detector for luggage control at airports, borders or at big
events. The handheld device 11 is touched at its handle 17 and hold
thereon during the measurement. Input keys 12 allow the selection
for example of various functions or are designed to start and end
the measurement operation. Measurement results may be metered
either acoustically, for example when excessing the detected
limits, or via reading the display 13.
[0067] FIG. 4 shows a further embodiment in which, according to the
invention, the cryo temperature cooling device is integrated to the
detector, forming one measurement device 9. Thereby the detector,
comprising a detector support 15 and a detector crystal 16
including pre-amplifier, the heat conducting element 4 and the
inner tank 5 together with the coolant 3 are forming a fixed
mounted device. Thereby, the heat conducting element 4 and the
detector support 15 can be made from one piece. The inner tank 5 is
made to withstand pressure in this embodiment, so that it can
withstand the vapor pressure of the used coolant at the maximum
operating temperature.
[0068] Via a connection 18, which may be protected and isolated by
a removable heat insulating cap 8, it is possible--after removal of
cap 8--to "load" the cryo temperature cooling device as described
above, that is it could be cooled, by keeping the heat conducting
contact of the connection 18 at a temperature T until the detector
is cooled and the coolant is mainly frozen. For the temperature T
it is true that T<T.sub.P, whereby T.sub.P is the phase
transition temperature of the coolant used according to the
invention. After removing the charging device from the connection
18 and attaching the protection cap 8, the detector is kept cooled
for several hours ready for operation.
[0069] FIG. 5 shows another embodiment, at which the "charging"
occurs not via the heat conducting element 4, but via a cooling
coil 19 mounted within the inner tank 5. Instead of the heat
conducting element 4, the cooling coil 19 is led to the connection
18, so that during the "charging process" the coolant 3 is cooled
via the cooling coil 19.
[0070] The use of cooling coil 19 for the charging of the cryo
temperature cooling device 1 is especially an advantage when cooled
(liquefied) gases, for example nitrogen or helium or others, liquid
coolants are available for the cooling process. Those cooled
(liquefied) gases or coolants could then be piped directly through
the inner part of the cooling coil, which allows for a higher heat
transport so that the cooling can take place faster. Furthermore,
the connections 18 of the cooling coil, being directed to the
outside, may consist of materials, being bad heat conductors, so
that the heat insulation of the cryo temperature cooling device
with regard to the surrounding is improved, so that the operation
time can even be improved with regard to the device shown in FIG.
4.
[0071] In addition to the use for the cooling of detectors, the
cryo temperature cooling device according to the invention can be
used in any devices where cryo temperatures are necessary or
wanted. This is especially true for, but not limited to further
measurement applications, not the least for such applications,
using superconductors, especially high Tc superconductors. One has
to think firsthand to electronics, here especially to noise
sensitive preamplifiers, to IR sensors, night vision devices, to
SQUIDs or to applications for radar.
LIST OF REFERENCES
[0072] 1 cryo temperature cooling device
[0073] 2 tank
[0074] 3 coolant
[0075] 4 heat conducting element
[0076] 5 inner wall (inner tank)
[0077] 6 outer wall (outer tank)
[0078] 7 intermediate space
[0079] 8 protecting cap
[0080] 9 measurement device
[0081] 10 detector
[0082] 11 handheld device
[0083] 12 input key
[0084] 13 display
[0085] 14 opening
[0086] 15 detector support
[0087] 16 detector crystal, eventually with preamplifier
[0088] 17 handle
[0089] 18 connection
[0090] 19 cooling coil
[0091] 20 outer wall of the detector
[0092] 21 radiation entry window
* * * * *