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Pulsing ion with transformer

IP.com Disclosure Number: IPCOM000247920D
Publication Date: 2016-Oct-11
Document File: 9 page(s) / 307K

Publishing Venue

The IP.com Prior Art Database

Related People

leonori: ATTORNEY

Abstract

The invention proposes the use of transformer drive for grid electrode of hot cathode minitron to realize same level of pulsing performance which has been achieved with totem-pole drive by limiting pulse with short and fixed, while adding various benefits of transformer drive.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 37% of the total text.

Page 01 of 9

Date:

12/09/2015

Title of Invention: Pulsing ion source with transformer

Inventor(s): T.Tajima, P. Wraight

OFSR Department:

ID No.: (inserted by IPL dept.)

Product Division: Princeton Technology Center

Summary of the Invention

The invention proposes the use of transformer drive for grid electrode of hot cathode minitron to realize same level of pulsing performance which has been achieved with totem-pole drive by limiting pulse with short and fixed, while adding various benefits of transformer drive.

Representative Figure

Figure 1: Transformer drive of grid electrode, circuit and waveform


Page 02 of 9

Field of Invention

This invention is pertinent to Pulsed Neutron Generators and their control electronics.

Key Words

PNG, Minitron, Ion Source, Grid, Cathode, Pulsing, Burst, Transformer

Prior Art

In pulsed neutron generator (PNG), the pulsed signal is applied to ion source of minitron in order to extract ionizing electrons from cathode electrode and eventually pulsed neutron is generated.

As the pulsed signal source, transformer-coupled driver has been used as drive circuit from 50's/60's in the tools such as TDT family. At that time, the minitron was 758 minitron which has penning (cold) cathode, and 2-3kV amplitude was required for driving pulse, so transformer was the most practical option to drive such a high voltage pulse.

Figure 2: Transformer drive for ion source

The drawback of transformer drive is the difficulty to achieve "support various pulse width" and "keep rising/falling time consistent" both in the same transformer. For those days of PNG, there was requirement to support various pulse width (50 ~ 400uS), but on the other hand, there was not so much demand for the stability of rising/falling time of driving signal because with penning cathode, start of ionizing pulse is unpredictable and pulse fall-off is inconsistent anyway.


Page 03 of 9

Figure 3: Current pulse of 758 penning cathode

So the design of the transformer was adapted to have acceptable droop with maximum pulse width, it means the rising/falling time were very slow. As the result, the driving waveform for short pulse width was close to triangular waveform, but it still satisfied the requirement.

After that, at the era of RST, 761 minitron which has hot cathode was introduced to downhole tools. Different from cold cathode, the rising/falling time of neutron pulse with hot cathode is fast and stable, and basically it directly reflects electrical pulse signal applied on grid electrode.

Figure 4: Current pulse of 761 hot cathode


Page 04 of 9

In addition, the required amplitude of pulse signal applied to grid electrode is 100-200V, much lower than the one in cold cathode. Thanks to this low drive voltage, it is possible to use two switch totem-pole drive with direct connection to the load, instead of transformer drive. The desired voltage for grid electrode is generated at pre-regulator in DC voltage, and this voltage is applied to grid electrode through upper s...