Sensor and method for simultaneously measuring pressure by crystal luminescence and velocity by laser Doppler interferometry

Abstract

Sensor and method for simultaneously measuring pressure by crystal luminescence and velocity by laser Doppler interferometry The invention relates to a sensor (1) for simultaneously measuring pressure and velocity comprising:- a crystal (2) comprising a face covered with a reflective layer (3),- a pumping laser (4) configured to emit a pumping beam (F1) towards the crystal and having a wavelength included in an absorption band of the crystal so that the illumination of the crystal by the pumping beam excites a portion of the electrons of the crystal,- a spectrometer (6) for receiving a luminescence signal (S1), resulting from a de-excitation of the electrons of the crystal, and for measuring the variation over time in wavelength of the lines of the light spectrum of said luminescence signal,- an interferometry system (12) configured to measure the variations in speed of the reflective layer over time by laser Doppler interferometry velocimetry. Figure for abstract: Fig. 1,

Description

Title of the invention: Sensor and method for simultaneously measuring pressure by crystal luminescence and velocity by laser Doppler interferometry Technical field

[0001] The present invention relates to the field of pressure sensors and that of speed sensors. In particular, the present invention relates both to the field of pressure sensors by crystalline luminescence, in particular by ruby ​​luminescence (PRL), and to the field of surface laser velocimeters, also called laser Doppler interferometry velocimeters (LIDL). Prior art

[0002] When studying the behavior of materials under extreme conditions, it is common to measure the pressure exerted on the material or the rate of deformation of the material. In particular, in the context of relatively slow compression tests, i.e., those lasting on the order of a second or even an hour, it is usual to measure the pressure exerted on the material. In the context of very rapid dynamic compression tests, i.e., those lasting on the order of a nanosecond, for example in the form of a shock wave, it is usual to measure the rate of deformation of the material.

[0003] A known method of pressure measurement is pressure measurement by crystalline luminescence, in particular pressure measurement by ruby ​​luminescence (PRL). Ruby is an alumina crystal A12O3 comprising chromium impurities and whose light absorption spectrum in the visible range has two distinct absorption bands, one around 407 and the other around 551 nm [1]. Pressure measurement by crystalline luminescence, in particular PRL, is based on the principle of natural fluorescence of a target crystal, for example ruby, sensitive to the pressure exerted on said crystal.

[0004] When the ruby ​​is irradiated in these absorption bands, some of its electrons become excited. This results in successive de-excitations of the excited electrons during which photons are emitted by the ruby; this phenomenon is called luminescence. This luminescence of the ruby ​​has two lines, called characteristic lines Ri and R2 of ruby ​​luminescence, with wavelengths for which the light intensity is maximum. At ambient temperature and pressure, these characteristic lines Ri and R2 of ruby ​​luminescence have, respectively, wavelengths of 694.25 nm and 692.85 nm.

[0005] A variation in pressure exerted on the ruby ​​causes a variation in length wavelength of the photons emitted by luminescence of the ruby. In particular, the wavelengths of the characteristic lines Ri and R2 vary depending on the pressure exerted on the ruby. Thus, the PRL measurement consists of measuring the variation in wavelength of the characteristic lines Ri and R2 over time and deducing the variation in pressure exerted on the ruby ​​over time.

[0006] Since the first static compression tests carried out with diamond anvil cells [2], PRL measurement has been commonly used to measure pressure variation during static compression tests, particularly in extreme conditions. Static compression tests are relatively slow, i.e. they are of the order of a second or even an hour.

[0007] Tests have been carried out to determine whether single-crystal rubies of different orientations are suitable for dynamic compression tests [3], [4], [5], [6] and [7]. However, the use of PRL measurement to measure the pressure exerted on a material during a dynamic compression test is not known.

[0008] During dynamic compression tests, it is usual to measure the deformation rate of the material and, if necessary, to deduce the pressure exerted by using known models.

[0009] A known method for measuring strain rate is surface laser velocimetry, also known as laser Doppler interferometry velocimetry (LDIV).

[0010] The VIDL measurement comprises illuminating a target surface with a laser and collecting the light reflected by said target surface by an interferometer in order to create interference from said reflected light. The movement of the target surface, in particular during the passage of a shock wave, induces a modification by Doppler effect of the optical frequency of the light reflected by the target surface. This variation in the optical frequency induces a variation in the interference created by the interferometer. It is thus possible to deduce the variation due to the Doppler effect of the optical frequency of the reflected light from the variation in the interference created by the interferometer and thereby determine the speed of the target surface over time.The VIDL measurement therefore includes the measurement of the temporal evolution of the interference created by the interferometer and the determination, from this measurement, of the speed of the target surface over time.

[0011] A common interferometer for performing a VIDL measurement is the velocity interferometer for any reflector, also called VISAR interferometer, for "Velocity Interferometer System for Any Reflector" in English [8]. The VISAR interferometer has the advantages of having high measurement accuracy and being non-intrusive.

[0012] Another interferometer known for performing a VIDL measurement is the Heterodyne Velocimetry (VH) interferometer, also called “Photon Doppler Velocimetry Interferometer” in English [9]. The VH interferometer has the advantage of being fully fibered and more compact. It is therefore simple to implement during experimental protocols.

[0013] VIDL measurement is often reserved for dynamic compression tests.

[0014] There are models of equations to calculate the speed of the ruby ​​from a measurement of pressure evolution by PRL, and, equation models allowing the calculation of the pressure exerted on a ruby ​​from a measurement of its speed by VIDL,

[10] ,

[11] ,

[12] and

[13] . However, there are uncertainties regarding the speeds and pressures deduced by these models.

[0015] There is therefore a need to overcome these uncertainties. More broadly, there is a need to know exactly the pressure exerted on a crystal and its speed over time during a test, particularly in compression, under extreme conditions.

[0016] In particular, there is a need for a device and / or a method making it possible to simultaneously measure the pressure exerted on a crystal and its speed during tests, in particular in static or dynamic compression.

[0017] The aim of the invention is to respond, at least in part, to this(these) need(s). Statement of the invention

[0018] To do this, the invention relates to a sensor for simultaneously measuring pressure and speed comprising: - a crystal comprising a face covered with a reflective layer, - a pump laser configured to emit a pump beam towards the crystal and having a wavelength included in an absorption band of the crystal such that the illumination of the crystal by the pump beam excites a portion of the electrons of the crystal, - a spectrometer for receiving a luminescence signal, resulting from a de-excitation of the electrons of the crystal, and for measuring the variation over time in wavelength of the lines of the light spectrum of said luminescence signal, - an interferometry system configured to measure the variations in speed of the reflective layer over time by laser Doppler interferometry velocimetry.

[0019] Preferably, the crystal is a ruby ​​crystal, preferably comprising a mass content of Cr3+ ions and / or chromium oxide of between 0.05 and 0.5%.

[0020] Preferably, the reflective layer is a silver layer.

[0021] Preferably, the reflective layer has a thickness of between 100 and 1000 nm.

[0022] Preferably, the pumping laser is a pulsed laser. Preferably, the pulsed laser is adapted to emit laser pulses of duration between 5 ns and 50 ps and / or of average energy between 1 and 1000 rnJ.

[0023] Preferably, the wavelength of the pump beam is between 500 and 560 nm.

[0024] Preferably, the sensor comprises a dichroic mirror transparent to the wavelength of the pump beam and configured to select a portion of the luminescence signal whose wavelength is within a predetermined range and direct only said selected portion towards the spectrometer. Preferably, the predetermined range extends from 680 nm to 720 nm.

[0025] Preferably, the spectrometer comprises: - a spectroscope configured to decompose the luminescence signal into a plurality of light lines distributed according to their wavelength, forming the light spectrum, and, - a photodetector to capture and record the light spectrum over time.

[0026] According to a first variant, the interferometry system may comprise: - a probing laser adapted to emit a probing beam towards the crystal so as to be reflected by the reflective layer after transmission through the crystal, - a heterodyne velocimetry interferometer adapted to create interference from the reflected part of the probing beam, called the probing signal, and to measure the temporal evolution of said interference.

[0027] According to this first variant, the sensor preferably comprises a dielectric mirror reflecting at the wavelength of the probing beam and transparent at the wavelength of the pumping beam, the dielectric mirror being arranged between the crystal and the pumping laser so as to direct the probing beam towards the crystal.

[0028] According to a second variant, the interferometry system may comprise a VISAR interferometer adapted to create interference from a probing signal, and to measure the temporal evolution of said interference, the probing signal being constituted by a part of the pumping beam by the reflective layer.

[0029] According to this second variant, the sensor preferably comprises a perforated mirror arranged between the crystal and the pumping laser so as to allow the pumping beam emitted by the pumping laser to pass towards the crystal and to redirect the part of the pumping beam, reflected by the reflective layer, towards the VISAR interferometer.

[0030] Preferably, the sensor comprises an optical lens adapted to focus the pump beam onto the reflective layer, and where appropriate, to focus the probing beam onto the reflective layer.

[0031] The invention also relates to a method for simultaneously measuring a pressure acting on a crystal and a speed of movement of said crystal, the crystal comprising a face covered with a reflective layer, the method comprising the following steps: a) illumination of the crystal by a pump beam having a wavelength included in an absorption band of the crystal so as to excite a part of the electrons of the crystal, b) emission of a luminescence signal resulting from de-excitation of the electrons in the crystal, c) measurement of the variation over time in wavelength of the lines of the light spectrum of the luminescence signal, and determination, from this variation, of the pressure exerted on the crystal over time, d) concurrently with steps a) to c), reception of a light signal, called a probing signal, resulting from the reflection of a laser beam on the reflective layer, and determination of the speed of the reflective layer over time by monitoring the temporal evolution of interference created from the probing signal.

[0032] Preferably, the method is implemented by a sensor according to the present invention.

[0033] The invention also relates to a use of a sensor according to the present invention or of a method according to the present invention, for a static or dynamic compression test, a pulsed electrical discharge test, a ballistic resistance test, in particular simulating the impacts of space debris in orbit, or a mechanical test in which the measured pressure and speed are induced by magnetic fields.

[0034] The present invention therefore essentially consists of a sensor and a method making it possible to simultaneously measure the evolution of the pressure exerted on a crystal and the speed of movement of said crystal, in particular during a static or dynamic compression test.

[0035] Thus, it is possible to link and compare the measured pressure and speed changes with each other in order to reduce measurement uncertainties. It is also possible to validate or invalidate certain equation models linking the pressure exerted on a crystal to the speed of said crystal. In addition, the crystal can be used as a gauge during a mechanical test of a material, particularly in extreme conditions.

[0036] Advantageously, the sensor according to the present invention may have a pumping laser adapted in power to allow rapid and sufficient excitation of the electrons of the crystal, for example of the order of a nanosecond or even less, so that said crystal emits, in less than 1 ns, a luminescence signal of sufficient intensity to be detected by the spectrometer, the temporal resolution of the spectrometer being less than 1 ns. Thus, the sensor is suitable for measuring the pressure exerted on the crystal during a dynamic compression test. Brief description of the drawings

[0037] Other advantages and characteristics will become more apparent upon reading the detailed description, given for illustrative and non-limiting purposes, with reference to the following figures:

[0038] [Fig-1] [Fig. 1] is a schematic view of a sensor for simultaneously measuring pressure and velocity according to a first embodiment of the invention in which the interferometry system for VIDL measurement comprises a probing laser and a VH interferometer;

[0039] [Fig.2A] [Fig.2A] represents the evolution over time of the light spectrum of the luminescence of a ruby, comprising 0.1% of chromium oxide, following its illumination by a pumping laser emitting a continuous beam of wavelength equal to 532 nm and power equal to 5 W;

[0040] [Fig.2B] [Fig.2B] represents the evolution over time of the light spectrum of the luminescence of a ruby, comprising 0.1% of chromium oxide, following its illumination by a pumping laser emitting laser pulses of wavelength equal to 532 nm, of duration equal to 10 ps and of average energy equal to 30 mJ;

[0041] [Fig.3] [Fig.3] represents the evolution over time, during a dynamic compression test, of the light spectrum of the ruby ​​luminescence captured by the spectroscope of a sensor according to the present invention;

[0042] [Fig.4] [Fig.4] is a schematic view of a sensor for simultaneously measuring a pressure and a velocity according to a second embodiment of the invention in which the interferometry system for the VIDL measurement comprises a VISAR interferometer. Detailed description

[0043] For reasons of clarity, the various elements of the figures are represented in free scale, the actual dimensions of the various parts not necessarily being respected.

[0044] [Fig.l] illustrates a sensor 1 for simultaneously measuring pressure and speed according to a first embodiment of the invention.

[0045] The sensor 1 comprises a crystal 2, one face of which is covered with a reflective layer 3. The crystal 2 is a ruby, that is to say an alumina crystal A12O3 comprising chromium impurities, for example in the form of Cr3+ ions and / or chromium oxide Cr2O3. Preferably, the crystal 2 is a ruby ​​comprising a mass content of Cr3+ ions and / or chromium oxide of between 0.05 and 0.5%, for example equal to 0.1%. The reflective layer 3 is made of silver and has a thickness of between 100 and 1000 nm.

[0046] The sensor 1 also comprises a pumping laser 4 configured to emit a pump beam Fi to crystal 2. Pump laser 4 is a pulsed laser suitable for emitting laser pulses with a duration between 5 ns and 50 ps and an average energy between 1 and 100 mJ.

[0047] The wavelength of the pumping beam Fi is included in one of the absorption bands of the crystal 2 so that the illumination of the crystal 2 by the pumping beam Fi excites a portion of the electrons of the crystal 2. In particular, the wavelength of the pumping beam Fi is included in the absorption band at 551 nm of the ruby, for example between 500 and 560 nm, preferably equal to 532 nm.

[0048] The use of a pulsed laser as a pump laser 4 in a crystal luminescence pressure measurement, in particular a PRL measurement, significantly increases the luminescence signal-to-noise ratio of the measurement. The pulsed laser also makes it possible to quickly emit a high-power pump beam Fi and thus obtain rapid and significant excitation of the electrons of the crystal 2.

[0049] The inventors produced light spectra of the luminescence signal of a ruby, comprising 0.1% chromium oxide, following its illumination by two different pumping lasers emitting a beam with a wavelength equal to 532 nm. Figures 2A and 2B represent the results of these tests.

[0050] [Fig.2A] shows the light spectrum, including the characteristic Ri and R 2 luminescence lines of ruby, obtained by a continuous pumping laser emitting a beam with a power of 5 W.

[0051] [Fig.2B] shows the light spectrum, including the characteristic Ri and R 2 luminescence lines of ruby, obtained by a pulsed pumping laser emitting laser pulses of duration equal to 10 ps and average energy equal to 30 mJ.

[0052] As can be seen from Figures 2A and 2B, the characteristic luminescence lines Ri and R 2 of the ruby ​​have a greater light intensity relative to the noise when the ruby ​​is illuminated by a pulsed laser compared to when the ruby ​​is illuminated by a continuous laser.

[0053] The sensor 1 also comprises an optical lens 5 for focusing the pumping beam Fi emitted by the pumping laser 4 onto the reflective layer 3, the reflective layer 3 covering the face of the crystal 2 opposite the face of the crystal 2 facing the optical lens 5. Thus, the beam Fi passes through the crystal 2 before being focused onto the reflective layer 3.

[0054] During its passage, the pump beam Fi excites a part of the electrons of the crystal 2 which then emits a luminescence signal Si, a part of which is recovered by the optical lens 5 and directed towards a spectrometer 6 included by the sensor 1.

[0055] The sensor 1 may comprise a dichroic mirror 7 configured to select the part S'i of the luminescence signal Si whose wavelength is included in a predetermined range and direct said selected part S'i towards the spectrometer 6, the remainder of the luminescence signal Si not being directed towards the spectrometer 6. The predetermined range comprises the wavelength lines for which the light intensity of the luminescence signal Si is maximum. Preferably, the predetermined range extends from 680 nm to 720 nm, it thus includes the characteristic luminescence lines Ri and R2 of ruby.

[0056] The spectrometer 6 is configured to measure the variation in wavelength of the lines of the luminescence signal received over time, in particular to measure the variation in wavelength of the characteristic lines Ri and R2 of luminescence of the ruby. For this purpose, the spectrometer 6 may comprise a spectroscope 8 configured to decompose the received signal into a plurality of light lines distributed according to their wavelength by forming a light spectrum, and a photodetector 9 to capture and record the light spectrum over time.

[0057] Preferably, the spectroscope 8 is configured so as to focus, during the decomposition forming the light spectrum, on the characteristic lines Ri and R2 of luminescence of the ruby.

[0058] Preferably, the photodetector 9 has a time resolution of less than 1 ns.

[0059] The photodetector 9 may be a slit-scanning camera, preferably comprising a multi-alkaline photocathode, preferably the photocathode being of the S25 type. Such a photodetector 9 has a very low temporal resolution, in particular less than 1 ns, and a high sensitivity for measuring the light intensity of the lines with a wavelength between 680 and 720 nm.

[0060] The spectrometer 6 may comprise an optical fiber 10, for conveying the part S'i of the luminescence signal Si selected by the dichroic mirror 7 to the spectroscope 8, and a connector 11, for injecting the part S'i of the luminescence signal Si into the optical fiber 10.

[0061] The sensor 1 may comprise a calculation unit for calculating the change in the pressure exerted on the crystal 2 over time from the variations in wavelength of the lines of the luminescence signal measured by the spectrometer 6.

[0062] [Fig. 3] illustrates the evolution in wavelength over time, during a dynamic compression test, of the characteristic lines RI and R2 of the ruby ​​luminescence measured by the spectroscope of the sensor 1 according to the present invention. As shown in this [Fig. 3], the sensor 1 has a time resolution suitable for measuring the pressure exerted on the crystal 2 during a dynamic compression test.

[0063] The sensor 1 also comprises an interferometry system 12 configured to measure the variations in speed of the reflective layer 3 over time by laser Doppler interferometry velocimetry (LDIV).

[0064] The interferometry system 12 comprises a probing laser 13 and a Heterodyne Velocimetry (HV) interferometer 14. The probing laser 13 is adapted to emit a probing beam F2 directed so as to be reflected by the reflective layer 3 after having been transmitted through the crystal 2. Preferably, the optical lens 5 focuses the probing beam F2 onto the reflective layer 3. Preferably, the wavelength of the probing beam F2 is between 1540 and 1560 nm, preferably equal to 1550 nm. Advantageously, the ruby ​​is transparent for these wavelengths.

[0065] The sensor 1 may comprise a dielectric mirror 15 reflecting at the wavelength of the probing beam S2 and transparent at the wavelength of the pumping beam Fi and at the wavelengths of the luminescence signal Sp. In particular, the dielectric mirror 15 is reflective in the infrared, in particular at 1550 nm, and transparent in the visible.

[0066] The dielectric mirror 15 is arranged so as to direct the probing beam F2 towards the crystal 2, in particular towards the optical lens 5 which focuses the probing beam F2 onto the reflective layer 3. In particular, the dielectric mirror 15 is arranged between the optical lens 5 and the pumping laser 4, where appropriate between the optical lens 5 and the dichroic mirror 7.

[0067] The reflection of the probing beam F2, called the probing signal S2, is recovered by the optical lens 5 and directed towards the interferometer VH 14. In particular, the probing signal S2 is reflected, after collimation by the optical lens 5, by the dielectric mirror 15 towards the interferometer VH 14.

[0068] The VH 14 interferometer is adapted to create interference from the sounding signal S2 and to measure the temporal evolution of said interference over time so as to deduce therefrom the variation in the speed of the reflective layer 3 over time.

[0069] The interferometry system 12 may comprise an optical fiber 16, for conveying the probing signal S2 coming from the dielectric mirror 15 to the VH interferometer 14, and a connector 17, for injecting the probing signal S2 into the optical fiber 16.

[0070] [Fig. 4] shows a sensor 1 for simultaneously measuring pressure and velocity according to a second embodiment of the invention. The sensor 1 of [Fig. 4] is similar to that of [Fig. 1] and differs from the latter in that the interferometry system 12 comprises a VISAR interferometer 18 in place of the probing laser 13 and the VH interferometer 14.

[0071] In the embodiment illustrated in [Fig.4] it is a part of the pump beam Fh reflected by the reflective layer 3, which serves as the probing signal S2.

[0072] The sensor 1 may comprise a perforated mirror 19 arranged so as to allow the pumping beam Fi emitted by the pumping laser 4 to pass towards the crystal 2 and to redirect the part of the pumping beam Fb reflected by the reflective layer 3 and forming the probing signal S2, towards the VISAR interferometer 18. In particular, the perforated mirror 19 is arranged between the pumping laser 4 and the optical lens 5, where appropriate between the pumping laser 4 and the dichroic mirror 7.

[0073] The VISAR 18 interferometer is adapted to create interference from the sounding signal S2 and to measure the temporal evolution of said interference over time so as to deduce therefrom the variation in the speed of the reflective layer 3 over time.

[0074] Other variants and improvements may be envisaged without departing from the scope of the invention as defined by the claims below. In particular, the present invention is not limited to ruby ​​as a crystal. Other crystals, having pressure-sensitive fluorescence during dynamic stresses, may be envisaged. List of cited references

[0075] [1] C. Degli Esposti et al.: “Absorption and emission spectroscopy of a lasing material: ruby”, Journal of Chemical Education, 84(8): 1316-1318, 2007.

[0076] [2] RA Forman et al.: “Pressure measurement made by the utilization of ruby ​​sharp- line luminescence”, Science, 176(4032): 284-285, 1972.

[0077] [3] PD Horn et al.: “Wavelength shift of the ruby ​​luminescence R Unes under shock compression”, Applied Physics Letter, 49(14): 856-858, 1986.

[0078] [4] Y.M. Gupta et al.: “Potential use of the r2 line shift for static high-pressure ca libration”, Applied Physics Letter, 58(6): 583-585, 1991.

[0079] [5] S.M. Sharma et al.: “Theoretical analysis of R-line shifts of ruby subjected to different deformation conditions”, Physical Review B, 43(1): 879-893, 1991.

[0080] [6] X.A. Shen et al.: “Effect of crystal orientation on ruby R-line shifts under shock compression and tension”, Physical Review B, 48(5): 2929-2940, 1993.

[0081] [7] J.K. Hyun et al.: “Ruby R-line for shock compression along (1102)”, Journal of Applied Physics, 84(4): 1947-1952, 1998.

[0082] [8] L.M. Barker et al.: “Shock-wave studies of pmma, fused, silica, and saphire”, Journal of Applied Physics, 41(4208), 1970.

[0083] [9] D.H. Dolan: “Accuracy and précision in photon doppler velocimetry”, Review of Scientific Instruments, 81(053905), 2010.

[0084]

[10] P.D. Horn et al.: “Luminescence R-line spectrum of ruby crystals shocked to 125 kbar along the crystal c axis”, Physical Review B, 38(2): 973-979, 1989.

[0085]

[11] V.N. Korobenko et al.: “Electrical resistivity and équation of State mea- surements on hot expanded aluminum in the metal-nonmetal transition range”, Physical Review B, 75(064208), 2007.

[0086]

[12] J. Clérouin et al.: “Direct measurements and ab initio stimulations for expanded fluid aluminum in the metal-nonmetal transition rage”, Physical Review B, 78(224203): 59-66, 2008.

[0087]

[13] L.D. Landau et al.: “Téorétitcheskaïa fizika v 10 tomakh : Tom IV Guidro- dinamika”, Mir - Ellipses, 3, isbn 2-7298-9423-3 édition, 1994.

Claims

Claims

1. Sensor (1) for simultaneously measuring a pressure and a speed comprising: - a crystal (2) comprising a face covered with a reflective layer (3), - a pumping laser (4) configured to emit a pumping beam (Fi) towards the crystal and having a wavelength included in an absorption band of the crystal so that the illumination of the crystal by the pumping beam excites a part of the electrons of the crystal, - a spectrometer (6) for receiving a luminescence signal (Si), resulting from a de-excitation of the electrons of the crystal, and for measuring the variation over time in wavelength of the lines of the light spectrum of said luminescence signal, - an interferometry system (12) configured to measure the variations in speed of the reflective layer over time by laser Doppler interferometry velocimetry.

2. Sensor according to claim 1, the crystal being a ruby ​​crystal, preferably comprising a mass content of Cr3+ ions and / or chromium oxide of between 0.05 and 0.5%.

3. Sensor according to claim 1 or 2, the reflective layer being a silver layer, preferably with a thickness of between 100 and 1000

4. llili. Sensor according to one of the preceding claims, the pumping laser being a pulsed laser, preferably adapted to emit laser pulses of duration between 5 ns and 50 ps and / or of average energy between 1 and 1000 mJ.

5. Sensor according to one of the preceding claims, the wavelength of the pumping beam being between 500 and 560 nm.

6. Sensor according to one of the preceding claims, comprising a dichroic mirror (7) transparent to the wavelength of the pumping beam and configured to select a part (S'i) of the luminescence signal whose wavelength is included in a predetermined range and direct only said selected part towards the spectrometer, preferably the predetermined range extending from 680 nm to 720 nm.

7. Sensor according to one of the preceding claims, the spectrometer comprising: - a spectroscope (8) configured to decompose the luminescence signal into a plurality of light lines distributed according to their wavelength, forming the light spectrum, and, - a photodetector (9) to capture and record the light spectrum over time.

8. Sensor according to one of the preceding claims, the interferometry system comprising: - a probing laser (13) adapted to emit a probing beam (F2) towards the crystal so as to be reflected by the reflective layer after transmission through the crystal, - a heterodyne velocimetry interferometer (14) adapted to create interference from the reflected part of the probing beam, called the probing signal (S2), and to measure the temporal evolution of said interference.

9. Sensor according to the preceding claim, comprising a dielectric mirror (15) reflecting at the wavelength of the probing beam and transparent at the wavelength of the pumping beam, the dielectric mirror being arranged between the crystal and the pumping laser so as to direct the probing beam towards the crystal.

10. Sensor according to one of claims 1 to 8, the interferometry system comprising a VISAR interferometer (18) adapted to create interference from a probing signal (S2), and to measure the temporal evolution of said interference, the probing signal consisting of a part of the pumping beam by the reflective layer.

11. Sensor according to the preceding claim, comprising a perforated mirror (19) arranged between the crystal and the pumping laser so as to allow the pumping beam emitted by the pumping laser to pass towards the crystal and to redirect the part of the pumping beam, reflected by the reflective layer, towards the VISAR interferometer.

12. Sensor according to one of the preceding claims, comprising an optical lens (5) adapted to focus the pumping beam on the reflective layer, and where appropriate, to focus the probing beam (F2) on the reflective layer.

13. Method for simultaneously measuring a pressure exerted on a crystal (2) and a speed of movement of said crystal, the crystal comprising a face covered with a reflective layer (3), the method comprising the following steps: a) illumination of the crystal by a pump beam (Fi) having a wavelength included in an absorption band of the crystal so as to excite a part of the electrons of the crystal, b) emission of a luminescence signal (Si) resulting from a de-excitation of the electrons of the crystal, c) measurement of the variation over time in wavelength of the lines of the light spectrum of the luminescence signal, and, determination, from this variation, of the pressure exerted on the crystal over time, d) concomitantly with steps a) to c), reception of a light signal, called probing signal (S2), resulting from the reflection of a laser beam on the reflective layer, and determination of the speed of the reflective layer over time by monitoring the temporal evolution of interference created from the probing signal.

14. Method according to the preceding claim, being implemented by a sensor according to one of claims 1 to 12.

15. Use of a sensor according to one of claims 1 to 12 or of a method according to claim 13 or 14, for a static or dynamic compression test, a pulsed electrical discharge test, a ballistic resistance test, in particular simulating the impacts of space debris in orbit, or a mechanical test in which the measured pressure and speed are induced by magnetic fields.

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