JPS63198248A - Particle beam modulating device - Google Patents

Abstract

PURPOSE:To freely change the time interval between a reference signal and a modulation signal by adding a delay circuit to a reference signal detecting system. CONSTITUTION:Ba 1 is heated by a crucible 2 to obtain a Ba molecular beam 3, which is chopper-modulated by a disk type chopper 4 rotating at 1000rpm. The modulation period is 6ms, and the molecular beam 3 is detected by a molecular beam detector 7 after the modulation. A reference signal is obtained by a sensor 6 at the symmetrical position with the beam 3. After Ba molecules are ionized and converted into electrons and multiplied, the signal is fed to a signal processing system constituted of a preamplifier 8, a discriminator 9, and a multi-channel analyzer 10. The reference signal becomes a trigger input signal to the analyzer 10 after passing a pulse waveform shaper 11, and a delay circuit 12. The circuit 12 can delay the signal by 0-9ms, and the rising signal of the signal waveform accumulated in the analyzer 10 can be set at any position in the whole period of 6ms. Accordingly, the interval between the reference signal and modulation signal can be freely changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a particle beam modulation device, and particularly to a signal processing system that makes it possible to set a modulation waveform to optimal observation conditions.

[Conventional technology]

In order to improve the S/N ratio of the particle beam signal or to measure the dynamic characteristics of the interaction between the particle beam and other materials, the particle beam is first modulated (mechanically chopped) and then the modulated signal and A common method is to extract synchronous or in-phase signals as output. A lock-in amplifier and a multichannel analyzer are used as an output signal processing system. Note that when modulating the particle beam, it is necessary to obtain a reference signal to clarify the start and end of the modulation.

[Problem that the invention seeks to solve]

In conventional output signal detection systems, the reference signal is used as a phase difference with respect to the output signal (lock-in amplifier) or as a trigger for output signal collection (multichannel analyzer).

In the conventional technology, the Journal of the Physical Society of Japan 1 and (1971-) No. 6
As described on pages 30 to 636, the reference signal and the particle beam signal during modulation are at a constant time interval due to their geometric arrangement, and this becomes a constant phase in the lock-in amplifier, and the multiplier In the channel amplifier, this is the rising point of the signal waveform.

The purpose of the present invention is to freely change the time interval between the reference signal and the modulated signal.6 [Means for solving the problem] The above purpose can be achieved by adding a delay circuit to the reference signal detection circuit. achieved.

[Effect]

Usually, modulation is performed by rotating a disk with one or more slots cut into it to chop the particle beam. Since the detection position of the reference signal is in a place other than the path of the particle beam, for example, in the case of one slot, the value obtained by dividing the distance Ω on the circumference between the two by the peripheral velocity V of the disk, that is, Q / v A time lag occurs between the reference signal and the particle beam signal.

When using two or more slots, the reference signal detector can be set geometrically so that when the first slot cuts the particle beam, the second slot detects the reference signal. However, there is a problem with accuracy.

In the present invention, a delay circuit is provided in the reference signal detection circuit to electrically correct this time difference. Furthermore, according to this method, time correction is possible regardless of the number of slots as long as they are equally spaced.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

In this embodiment, Bal is used as a particle beam source, and a Ba molecular beam 3 is obtained by heating a crucible 2 made of boron nitride.

Molecular beams are molecules ejected from a nozzle in the case of a gas, molecules ejected from a nude sensor cell as in this example in the case of a substance with a low melting point and high vapor pressure, and electron beam bombardment in the case of a substance with a high melting point and low vapor pressure. Molecules produced by heating the mold are used in each case.

It is also possible to use ions or the like as the particle beam. Note that both operate in a vacuum.

The Ba molecular beam 3 is chopped and modulated by a disk-shaped chopper 4. This chopper 4 is provided with ten slots with openings and closing portions spaced at equal intervals. The chopper 4 is driven by a motor 5 and rotates at a speed of 1000 r, pm. Therefore, the modulation period is 6ms. The reference signal is obtained from a sensor 6 called a photocoupler, which is an integrated structure in which a light emitting diode and a photodiode face each other, and this sensor 6 is installed at a position symmetrical to the Ba molecular beam 3. After being modulated, the Ba molecular beam 3 flies in a vacuum and is detected by a molecular beam detector 7.

In this example, a quadrupole mass spectrometer (not shown) was used,
Ba molecules are ionized, converted into electrons and multiplied by an electron multiplier, and then the signal is supplied to a signal processing system. The signal processing system includes a preamplifier 8, a discriminator 9, and a multichannel analyzer 10.

On the other hand, the reference signal becomes a trigger input signal of the multi-channel analyzer 10 after passing through a pulse shaper 11 and a delay circuit 12. Only when a trigger signal is received, the gate of the multi-channel analyzer is opened and the signal is input.

The delay circuit is manufactured to enable a delay of 0 to 9 ms, and has an accuracy on the order of μS. As a result, the rising position of the signal waveform stored in the multichannel analyzer 10 can be set at any position within the total period of 6 ms.

〔Effect of the invention〕

According to the present invention, it is possible to set the signal waveform so that it can be observed in an optimal state, and subsequent signal analysis becomes extremely easy.

Furthermore, when the present invention is applied to signal detection using a lock-in amplifier, the phase shift of the signal can be corrected by the delay circuit, making it easy to measure the phase of the signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Ba molecule source, 2... Crucible, 3... Ba molecular beam, 4... Chopper, 5... Motor, 6... Sensor, 7... Molecular beam detector, 8 ...Preamplifier, 9
... Discriminator, 10... Multi-channel analyzer, 11... Pulse shaper, 12... Delay circuit. 3 Bad dialect σ line 4 Kori・/ha. 2 Yansa 7 Line Orange Earthenware lθ Maru + Beginful Threat Q Itoiwa L II To 0 Lus Shaped Eyebrow [12i Extension Circuit

Claims (1)

[Claims] 1. A particle beam modulation device characterized by adding a delay circuit to a reference signal detection system. 2. The particle beam modulator according to item 1, characterized in that a delay time longer than the modulation period is possible.