CN1219312C - Femto second heavy current high brightness electron microscope device - Google Patents
Femto second heavy current high brightness electron microscope device Download PDFInfo
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- CN1219312C CN1219312C CN 03115583 CN03115583A CN1219312C CN 1219312 C CN1219312 C CN 1219312C CN 03115583 CN03115583 CN 03115583 CN 03115583 A CN03115583 A CN 03115583A CN 1219312 C CN1219312 C CN 1219312C
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- Prior art keywords
- laser
- femtosecond
- femto
- microscope device
- electron microscope
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Abstract
The present invention relates to a femtosecond electron microscope device with strong current and high brightness, which is characterized in that the femtosecond electron microscope device is composed of two parts; the first part is orderly composed of a femtosecond laser, a filter and a lens assembly; the second part comprises a light cathode, an accelerating anode, an electromagnetic lens and a receiver fluoroscopic screen in a vacuum casing; the femtosecond laser is an Nd: YAG double frequency laser; the filter is used for adjusting the output power density of the femtosecond laser; the lens assembly is an achromatized lens assembly; the light cathode is made of a metal compound LaB6. The femtosecond electron microscope device can operate in a continuous state, can also work in the state of high repetition frequency and femtosecond ultrashort pulses and can be used for observing various ultrafast processes.
Description
The band technical field:
The present invention relates to the pulsed electron microscopie unit, particularly a kind of femtosecond heavy current high brightness electronic microscope.
The band background technology:
Electron microscope has obtained in micro-field to use extremely widely, has been a widely known industry, no matter in units such as hospital, industrial and agricultural production department, national defence, colleges and universities, research institutes, has also become an indispensable instrument.
Regrettably, present electron microscope can only be worked in a continuous manner, can only be used for studying and observing some static problems, says that in some sense this has seriously influenced its development.
The band summary of the invention:
The present invention is directed to the shortcoming of above-mentioned technology formerly, propose a kind of employing femtosecond intense laser pulse driving photocathode and equip electron microscope, the Laser Driven photocathode is based on the photoelectric effect principle, and the brightness of electron beam is:
B＝J
c/π
2ε
n 2
ε
n＝r(2ΔE/m
0c
2)
1/2
In the formula: m
0Be electron rest mass, m
0=9.109 * 10
-31Kg;
C is the light velocity, C=2.9979 * 10
8M/s;
Δ E is the energy bandwidth, Δ E=0.20eV;
R is the emission radius.
Material as photocathode has three classes usually:
(1) metal species mainly contains gold, copper, magnesium, tantalum etc., and its characteristic is a threshold value merit height, and quantum efficiency is low, because most of incident optical energy converts heat energy to, the photocathode that high-repetition-rate is turned round needs cooling; Advantage is easy preparation, and long service life is low to the vacuum degree requirement, is generally 10
-5～10
-8
(2) metallic compound and alloy typically have LaB
6, higher quantum efficiency is arranged, ultraviolet band there is higher sensitivity, require also low to vacuum degree.
(3) semiconductor photocathode.It mainly is the polybase antimonide material.As: Cs
3Sb, CsK
2Sb and GaAs etc.The quantum efficiency of semiconductor photocathode is the highest, can reach 2～8%; The threshold value merit is lower, can obtain higher current density.Unique shortcoming is that the life-span is short, has only tens hours.(referring to document: Chen Jianwen, Ou Yangbin, the king Zhijiang River, the light laser technical progress, 1992, the 3rd volume, 1-5).
Must from above-mentioned three class materials, make one's options according to the combination property of each side such as the threshold value merit of the wavelength of employed femtosecond laser, required photocathode and quantum efficiency in the reality.Here we select the metallic compound of long service life to make photocathode.
The problem to be solved in the present invention is to overcome above-mentioned the deficiencies in the prior art, a kind of femtosecond heavy current high brightness electronic microscope device is provided, it can operate at continuous state, can be used for observing various ultrafast processes with high repetition frequency and the work down of femtosecond ultrashort pulse state again.
Technical solution of the present invention is as follows:
A kind of femtosecond heavy current high brightness electronic microscope device is characterized in that it is made up of two parts, is followed successively by femto-second laser, filter and the set of lenses of first; Second portion is photocathode, accelerating anode, electromagnetic lens and the receiver phosphor screen in a vacuum casting; Said femto-second laser is Nd:YAG two frequency double lasers, and said filter is used for regulating the output power density of femto-second laser, and said set of lenses is through achromatic set of lenses, and said photocathode adopts metallic compound LaB
6Make, said accelerating anode, electromagnetic lens are the parts of the same type in the ordinary electronic microscope.
Said femto-second laser is Nd:YAG two frequency double lasers, is the threshold value merit that radiation wavelength or photon energy are greater than photocathode material to its requirement, and its two frequency multiplication photon energies are 2.33eV (530nm).This laser can continuous operation, again can be with femtosecond pulse work.Running hours is convenient to the staff and is regulated electron microscope, moves under pulse condition, is used for taking dynamic micrograph.When under the high repetition frequency state, turning round, can be used to the research trends process.The supposition laser pulse duration is 500 femtoseconds now, output energy 50nj, and power density then is: 10
5W/cm
2, corresponding number of photons is 2.67 * 10
13/ cm
2, the quantum efficiency of supposing photocathode is 10
-2, the electron number that obtains is 2.67 * 10
11/ cm
2, the corresponding quantity of electric charge is 42nc, peak current I=Q/C=2000A/cm
2
Compare with technology formerly, femtosecond heavy current high brightness electronic microscope of the present invention can operate at continuous state, can be used for observing various ultrafast processes with high repetition frequency and the work down of femtosecond ultrashort pulse state again.Because the pulse duration can be short to the femtosecond magnitude, therefore, to the machinery of electron microscope, power supply stability, the requirement of stray EM field, space shielding is reduced greatly.
Description of drawings:
Fig. 1 is a femtosecond heavy current high brightness electronic microscope structural representation of the present invention.
Embodiment:
Femtosecond heavy current high brightness electronic microscope device of the present invention as shown in Figure 1.Comprise femtosecond Nd:YAG laser 1, filter 2 and the achromatic lens 3 that places atmosphere and place the interior photocathode 4 of vacuum casting, accelerating anode 5, electromagnetic amplifying lens group 6, receiver phosphor screen 7.
Femtosecond Nd:YAG laser 1 is that a pulsewidth is that 500 femtoseconds, output energy are 50nj, two frequency double lasers, it is made up of an oscillator and an amplifier, frequency-doubling crystal adopts KDP, and mating plate 2 is finished after filtration, incides on the achromatic lens 3, through its focusing, incide on the photocathode 4, produce photoelectron, photoelectronic energy bandwidth is:
ΔE＝1/2(E
L-φ)
In the formula, E
LBe the laser photon energy, φ is the work function of photocathode, and photoelectron is amplified on the arrival phosphor screen 7 Direct observation or shooting after quickening through accelerating anode 5 again by electromagnetic lens 6.
Claims (2)
1, a kind of femtosecond heavy current high brightness electronic microscope device, comprise ultrashort pulse laser, light focusing element, vacuum target chamber, the electronic imaging parts, the image receiving-member, it is characterized in that described ultrashort pulse laser is femto-second laser (1), described light focusing element is set of lenses (3), described vacuum target chamber is vacuum casting (8), described electronic imaging parts are electromagnetic lens (6), described image receiving-member is receiver phosphor screen (7), the overall formation of apparatus of the present invention is made up of two parts, is followed successively by the femto-second laser (1) of first, filter (2) and set of lenses (3); Second portion is photocathode (4), accelerating anode (5), electromagnetic lens (6) and the receiver phosphor screen (7) in a vacuum casting (8); Said femto-second laser (1) is Nd:YAG two frequency double lasers, the output power density that said filter (2) is used for regulating femto-second laser, said set of lenses (3) is through achromatic set of lenses, and said photocathode (4) adopts metallic compound LaB
6Make, said accelerating anode (5), electromagnetic lens (6) are the parts of the same type in the ordinary electronic microscope.
2, femtosecond heavy current high brightness electronic microscope device according to claim 1 is characterized in that described femto-second laser (1) can continuous operation, again can be with high repetition frequency and femtosecond ultrashort pulse work.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 03115583 CN1219312C (en) | 2003-02-28 | 2003-02-28 | Femto second heavy current high brightness electron microscope device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 03115583 CN1219312C (en) | 2003-02-28 | 2003-02-28 | Femto second heavy current high brightness electron microscope device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1448980A CN1448980A (en) | 2003-10-15 |
| CN1219312C true CN1219312C (en) | 2005-09-14 |
Family
ID=28684139
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 03115583 Expired - Fee Related CN1219312C (en) | 2003-02-28 | 2003-02-28 | Femto second heavy current high brightness electron microscope device |
Country Status (1)
| Country | Link |
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| CN (1) | CN1219312C (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7154091B2 (en) | 2004-04-02 | 2006-12-26 | California Institute Of Technology | Method and system for ultrafast photoelectron microscope |
| CN100423170C (en) * | 2005-04-22 | 2008-10-01 | 中国科学院物理研究所 | Electron beam generating and controlling device |
| CN101404237B (en) * | 2008-09-01 | 2010-06-16 | 西安理工大学 | Image intensifier for improving detection performance of low-light level imaging system at normal temperature |
| CN101964289B (en) * | 2010-08-25 | 2012-05-30 | 北京中科科仪技术发展有限责任公司 | Method for manufacturing acceleration pole for transmission electron microscope and ceramic rings thereof |
| CN114252653B (en) * | 2021-01-06 | 2023-12-12 | 中国科学院物理研究所 | Ultrafast imaging device and method thereof |
-
2003
- 2003-02-28 CN CN 03115583 patent/CN1219312C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| CN1448980A (en) | 2003-10-15 |
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Granted publication date: 20050914 Termination date: 20100228 |