Author Topic: Faxitron MX-20 Reverse engineering (with some good results)  (Read 18722 times)

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Offline Manawyrm

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #50 on: January 21, 2022, 10:27:19 pm »
Quote
I had to build my own digitizer

Heh, yeah, I'll have to do the same thing. I had to download the pictures manually (seems to be a HTTPS->HTTP thing).
Very nice board!

I haven't checked yet whether my machine uses the RadEye 1 or 2 sensor. It seems to be the DC44 option model.
Will open it soon.

My current plan was to use one of the modern STM32H7 processors, save an image to SDRAM and then either use SPI or something else to get the picture onto my computer.
 

Offline Manawyrm

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #51 on: January 22, 2022, 01:20:59 am »
@KE5FX:
You wouldn't happen to have one or two raw 14-bit images, that I could use for developing my user interface while I'm waiting for my acquisition hardware?
Just any format (binary, csv, etc.) would be totally fine, I can make that work :)
 

Online KE5FX

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #52 on: January 22, 2022, 01:45:33 am »
@KE5FX:
You wouldn't happen to have one or two raw 14-bit images, that I could use for developing my user interface while I'm waiting for my acquisition hardware?
Just any format (binary, csv, etc.) would be totally fine, I can make that work :)

No, my application reads the data into memory and saves it in .png format, so there is never a raw image file anywhere.  It's a giant hack, feel free to snag anything you want out of it.   (Probably need to enable non-https transfers for that link as well.)
 

Offline LaserSteve

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #53 on: January 23, 2022, 03:59:59 am »
Seasoning in rotating anode tubes is done to 1. Getter the vacuum to prevent flash over. 2. Uniformly heat the whole rotating anode to prevent mechanical stress. 3. Clean the surface of the anode. 4 Bring the cooling oil to uniform temperature. 5.. Clean the bus bar tracks and brushes  on the rotating gantry to ensure clean power delivery.

Failing to season the tube prior to imaging
Was a instant dismissal offense.
Seasoning adds greatly to tube lifetime.

In larger systems an anode heat capacity calculator is running in the background, to protect the tube.

There was only one accepted excuse. If you were in the field
working on a system and an accident victim came in,
If the ER physician and the radiology technician so ordered, you could skip calibration and seasoning to try to save a life.

I spent a year training to be a  medical CT repair instructor. The FDA shut down my employer's plant for a year, so I moved on.

Steve
« Last Edit: January 23, 2022, 04:41:41 am by LaserSteve »
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Online KE5FX

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #54 on: January 23, 2022, 06:25:16 am »
Seasoning in rotating anode tubes is done to 1. Getter the vacuum to prevent flash over. 2. Uniformly heat the whole rotating anode to prevent mechanical stress. 3. Clean the surface of the anode. 4 Bring the cooling oil to uniform temperature. 5.. Clean the bus bar tracks and brushes  on the rotating gantry to ensure clean power delivery.

Sure, for a high voltage, high power rotating-anode tube.  But this machine has a fixed-anode 35 kV tube, with dissipation in the 10-watt neighborhood.   :-//  I don't get what seasoning does, other than to accelerate tube wear.  Do tubes this wimpy ever suffer from flashover?
 

Offline LaserSteve

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #55 on: January 24, 2022, 07:27:11 am »
Yes, most x-ray  tubes do suffer from random outgassing.
It does not take much gas to transition from e-beam to arc.
Tungsten or other refractory metal  anodes are sintered from powder in a press under extreme pressure and temperature.  For that reason they tend to store tiny pockets of gas. Using the heated cathode as an active getter strikes me as asking for trouble. But that is the designer's problem.

Steve


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Offline LaserSteve

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Online KE5FX

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #57 on: January 24, 2022, 10:25:54 pm »
That article might "settle it" for some unspecified classes of tubes, but as usual, it fails to acknowledge the massive difference in construction and operating conditions between a 35 kV microfocus tube and a high-power rotary anode tube operating at hundreds of kV.  It's like comparing a 4CX100000 to a 6AQ5.  There is, again as usual, nothing type-specific to go by in this article, which is my whole beef.

The procedure in the article also bears little to no resemblance to the procedure in the docs I got with the MX20.  You can't adjust the tube current on the MX20, for example, only the voltage... and the operating note says to do it every day, not every 3 months.

While I might prefer the 3-month advice given here because it's less trouble than doing it every day, I still don't have any reason to think it applies.  Maybe it's more important to season a low-power microfocus tube frequently.  Dunno.
 

Offline LaserSteve

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #58 on: January 25, 2022, 12:23:53 am »
The page above  referenced two of their micro tube numbers. Perhaps ask either Oxford or X-Ray-Worx via email?

My Googl-Fu is decent, I could find almost no detail on seasoning or conditioning microfocus tubes.

After reading up on them, I'm intrigued.   We have one in a mouse/rat scanner downstairs at work.  One of the few instruments in my building I've never toyed with.  I'll see if I can get my hands on the manual.



Steve
« Last Edit: January 25, 2022, 12:27:07 am by LaserSteve »
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Online Fraser

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #59 on: January 25, 2022, 12:50:32 pm »
The Faxitron Microfocus tube is made by TruFocus and their datasheet for the tube includes a warranty comment about treating the tube correctly in accordance with their use guides. It may be worth asking the people who actually manufacture this specific tube ?
If you are lucky, they will provide the tube integration guide that should include operational care procedures.

The tube is a TruFocus 8050 side window model.

http://www.trufocus.com/xray_datasheets/microfocus/8000-SWS-Side%20Window/8050%20SWS/MFX-8050-SWS-V01.pdf

TruFocus support POC: info@trufocus.com

My understanding of the need for seasoning was that if gas purity within the tube. A flashover can be catastrophic for the machine and these cost £60K in the UK so I can understand why the users are told to regularly season the tube. As a basic rule, the MX-20 was to be warmed up each day and seasoned on a specified kV for 300 Seconds. This got everything warmed up nicely ready fir the working day. It would also reveal any serviceability issues in the machine as some of these were mission critical in operating theatre for removed tissue X-Ray inspection. Of note, the kV setting fir the conditioning run varied over different user manual generations. It used to be 22kV, then 20kV and I have seen 18kV hand written over the manuals 20kV in one manual.

My take on the conditioning cycle was that it gave the machine time to warm up a bit and settle down fir my imaging run. 300 Seconds was not very long to wait and the digital camera plate takes up to 30 minutes to completely warm up and settle down, if doing a calibration, so in the big scheme of things, the conditioning cycles not an issue fir me. If I had not used the machine for a few weeks I would go as far as running conditioning cycles of 300 Seconds duration at 10kV, then 15kV, then 20kV and finally 30kV. After that treatment I could be sure that the tube was nice and warm ready for it’s work. The wear on the tube was minimal but the benefit was potentially significant so I chose to treat my MX-20 machines with great care to prolong the tube life. A failed tube was normally a ‘end of life’ event for a MX-20 as the TruFocus tube was horrendously expensive. IIRC it was £5K. Why take a chance of harming the tube by not following the Faxitron tube care guidance ?

Fraser
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Offline BUAROD

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #60 on: January 28, 2022, 09:36:59 am »
@kilohercas:

Regarding the Hamamatsu sensor C9732DK I found this statement in your post:

It can work with 100kV. In my work, i get visit from Hamamatsu, he says that problem with energy and power is that CsI will get yellow in time, but that's not a problem, since we still have so much data to work with, and we could use higher exposure times to get higher pixel values, so detector will be good for a long time.


I think about replacing the TFX-8035 tube in my MX-20 e.g with a PXS10 system, which allows up to 130kV anode voltage.
Beside necessary additional shielding I am concerned what will happen to the C9732DK? What do you think?
Do you have more information than already written from Hamamatsu?
Remark: the MX-20 is not intended to be used in continuous operation but may be once a month ... 
Many thanks in advance!
 

Offline LaserSteve

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #61 on: January 28, 2022, 03:34:57 pm »
As you move to a higher power tube, you might find you need to add filters for spectral correction on the tube output if scanning organics and polymers. Higher acceleration causes spectral broadening at the source. So if it's an organic or polymer target, you can generate far more x-ray photons in a region that is not absorbed, and this could add noise to your detector that obscures  weak signals. This results in a nonlinear gamma curve in organics/polymers.

With a hotter tube, you will also  get much more scatter off the shielding  into the detector.


JUST FYI:


In  living things, of course the goal was to tailor the spectrum to specific adsorption to reduce irradiation in the patient, achieve high contrast based on atoms present in the tissue,  and reduce patient exposure to useless low energy photons. Another major consideration was designing the filter to extend scintillator lifetime. Something to think about if your imaging "soft" materials. 


FyI:

Probably not an issue with a micro-focus tube, but with larger anodes the filters were shaped to correct for the beam pattern at the detectors. Ie get rid of the Hotspot in the center and wasted energy outside the detector area that resulted in scatter that reduced contrast.

Filters in my case were stacks of nylon blocks, then thin copper, aluminum, and beryllium sheets

Steve
« Last Edit: January 28, 2022, 04:19:39 pm by LaserSteve »
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Offline BUAROD

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #62 on: January 29, 2022, 01:08:36 pm »
Thank you Steve for the quick reply!

My area of ​​application is more the analysis of defective parts or assemblies, where I would like to see, for example,
the solder balls under a BGA or the bonding wires in an IC. The 35kV are obviously not nearly enough.
This issue has been raised several times here on the forums, but I haven't found a way to upgrade the MX-20 for this application.

Does anyone have an idea or has this already implemented?
 

Offline danielbriggs

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #63 on: January 29, 2022, 01:42:08 pm »
The 35kV are obviously not nearly enough.
This issue has been raised several times here on the forums, but I haven't found a way to upgrade the MX-20 for this application.

Does anyone have an idea or has this already implemented?

I asked this question to MikesElectricStuff last night on the EEVBlog Live stream, and he quite correctly pointed out the Hamamatsu sensor isn't rated past 35kV, so pushing the MX-20 past 35kV would be expensive and quite involved.
 

Offline LaserSteve

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #64 on: January 29, 2022, 07:24:33 pm »
Golden Engineering makes some point source systems that might be useful for close in PCB inspection.

Steve
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Online KE5FX

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #65 on: January 29, 2022, 09:18:14 pm »
Thank you Steve for the quick reply!

My area of ​​application is more the analysis of defective parts or assemblies, where I would like to see, for example,
the solder balls under a BGA or the bonding wires in an IC. The 35kV are obviously not nearly enough.
This issue has been raised several times here on the forums, but I haven't found a way to upgrade the MX-20 for this application.

Does anyone have an idea or has this already implemented?

Whether 35 kV is enough depends on several things, most prominently the atomic number of the material you're shooting through and how much of it there is.  35 kV is enough to obtain photos like the ones in the other thread, many of which are on par with commercial X-ray PCB inspection systems. 

What the commercial inspection systems buy you is the ability to see through more layers of copper.  8 layers of 1-oz copper is about as far as I can push my own MX-20.  That's sufficient for the vast majority of boards I work with.

The MX-20 has incredible resolution, enough to make bond wires look like heavy cables.



Of course you can only tell so much about BGA assembly quality by looking straight down at the ball-PCB interface once the beam has had to travel through the much thicker balls themselves.  Stray blobs of solder will stand out nicely, for sure.

You can 'overclock' the MX20 to about 37 kV, and I do think that's worthwhile, but going all the way to 50 seems inadvisable at first glance even though the tube itself is rated for it.  The need for a careful radiation survey would go without question, and you'd have to back off the anode current substantially to avoid damaging the tube.
 

Offline mikeselectricstuff

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #66 on: January 29, 2022, 10:31:27 pm »

You can 'overclock' the MX20 to about 37 kV, and I do think that's worthwhile, but going all the way to 50 seems inadvisable at first glance even though the tube itself is rated for it.  The need for a careful radiation survey would go without question, and you'd have to back off the anode current substantially to avoid damaging the tube.
ISTR reading somewhere that the Hamamtsu sensor was only rated to 35kVp
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Offline LaserSteve

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #67 on: January 30, 2022, 05:29:27 am »
I realize that all you can control on the Faxitron is voltage and exposure time, and probably some other detector parameters. However this is still worth a read.  I'm used to having time, mAS and KvP controls. In my world not having tube current control would really be depressing. Going from 35 to 37 Kv is only a 6% change.

This page has a really good explanation of some basic relationships.

https://howradiologyworks.com/xraycalc/

Steve.
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Online KE5FX

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #68 on: January 30, 2022, 05:49:34 am »
Going from 35 to 37 Kv is only a 6% change.

The article points out that exposure is proportional to the fifth power of the voltage, though.  ("Since x-ray exposure goes approximately as kVp5 and we generally don’t think in powers of 5 a well known approximation is typically used called the 15% rule of kVp of radiography. This rule comes from the fact that 1.155 ~2.0. Therefore, for each increase of 15% in kVp the exposure will double. Thus, if the kVp is increased by 15% then the mA must be decreased by a factor of 2 in order to maintain constant exposure on the image receptor. ")

I'll confess I don't understand where this relation could possibly come from.  kVp is the spectral location of the bremsstrahlung peak, and mA is its height, isn't it?  What's the physics behind the fifth-power dependency of exposure on anode voltage?
 

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Offline LaserSteve

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #70 on: January 30, 2022, 07:56:40 pm »
I need to pull a paper out of the library at work on Monday to get a good explanation of that 5th power rule.. It's the whole chain of transfer functions, both source and detector. It's more film oriented, but it does apply to a detector structure that does not apply signal processing to the image.

Monday...

Steve
« Last Edit: February 02, 2022, 08:12:47 pm by LaserSteve »
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Offline LaserSteve

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #71 on: February 02, 2022, 08:11:45 pm »




From:

G.S. Al-Balool, D.L. Newman,
The relationships between kV, mAs and thickness in film-based radiography: 25% and 15% rules. OK?,
Radiography,
Volume 4, Issue 2,
1998,
Pages 129-134,
ISSN 1078-8174,
https://doi.org/10.1016/S1078-8174(98)90009-8.
(https://www.sciencedirect.com/science/article/pii/S1078817498900098)

Abstract: Purpose: To investigate the validity of the 25% and 15% rules in manual exposure selection. Methods: The mAs required to produce a constant film density of 1.5 was determined over the X-ray tube potential range 50–150 kV for different thicknesses of water, under grid and no grid conditions. Results: The mAs change is an exponential function with depth and is dependent upon the attenuation coefficient. The 25% rule assumes a constant attenuation coefficient with a half value layer (HVL) equal to 3 cm. The results indicate that for non-grid work at low X-ray tube potentials and for grid work at higher tube potentials the 25% rule is applicable. The 15% rule implies an inverse power relationship between mAs and tube potential, the power term being 5. The results indicate that for both grid and no grid conditions the 15% rule is obeyed only over the tube potential range 50–100 kV and for thicknesses up to 15 cm. Discussion: The 25% and 15% rules have provided useful practical guidelines for exposure factor selection. It is shown that they are applicable to some but not all radiographic situations.
Keywords: exposure factors; selection; 25% rule; 15% rule


Simplified Conclusion of the paper: 15% rule holds for tissue of less then 13 cm thickness and Voltages less then 100 kV.
For other more drastic conditions the 20$% rule holds.

I quote:

" In fixed kV techniques, the 25% rule is widely
applied [1, 2]. This states that for every I cm
change in patient thickness a 25% mAs change is
required. This rule derives from the exponential
attenuation relationship in that the required mAs
change is proportional to e ^ ±Hx where His the
attenuation coefficient and x the thickness, the sign
depending on whether an increase or decrease in
mAs is required, i.e. whether there is an increase or
decrease in patient thickness. Therefore, as the
thickness changes the mAs needs to be changed
exponentially to maintain constant film blackening.
For the 25% per cm rule to apply over the whole
range of diagnostic tube potentials,/a is assumed to
remain constant and equal to 0.23I c m - ~ i.e. a half
value layer (HVL) for soft tissue of 3 cm. This, of
course is a simplification since 1~and hence HVL are
energy dependent. However, the mAs stations
on many X-ray units today follow this rule in that
each consecutive mAs step represents a change of
25%. Thus, in fixed kV techniques, thickness
changes can be compensated by appropriate step
changes in mAs."

For the 15% rule:

I quote

"In variable kV techniques the situation is not as
straightforward because there are a number of kV
dependent changes that take place when the tube
potential is varied. These include changes in tube
output, X-ray attenuation (absorption and scatter)
and film screen speed. At a given patient thickness,
adjustment of the tube potential requires a compen-
satory adjustment in mAs so that the resultant
exposure produces the same level of film blacken-
ing. The so-called 15% rule [3-6] has been used as
a guide to the change in mAs that is required. This
rule states that to achieve the same film blackening,
a 15% change in kV requires a compensatory
change in mAs of a factor of 2. If an inverse power
relationship exists between mAs and tube poten-
tial, this rule assumes that the power term is 5,
since 1.15s=2, i.e. mAscz kV -5. This rule results
from the relationships between mAs and tube
potential in determining X-ray output, attenuation
and film screen response. With the introduction of
high frequency generators and energy-dependent
intensifying screens it is possible that these rela-
tionships have changed and hence the rules may
now not be applicable or at least need to be
amended"

REFERENCES for above PAPER:

A Kelly
Black or white?—hit or miss?
The Radiographer, 35 (1988), pp. 19-26
View Record in ScopusGoogle Scholar
2.
Why exposure tables with a point system?, Siemens Radiographic World News (1962)
Siemens
Google Scholar
3.
RR Carlton, A Adler
Principles of Radiographic Imaging
Delmar Publishers Inc, Albany (1992), pp. 480-481
Google Scholar
4.
JC Malott, J Fodor
The Art and Science of Medical Radiography
(7th edn.), Mosby Year Book Inc, St Louis (1993), pp. 130-131
Google Scholar
5.
QB Carroll
Radiographic Exposure, Processing and Quality Control
(5th edn.), Charles Thomas, Springfield (1993), pp. 102-106
CrossRefGoogle Scholar
6.
JE Wallace
Radiographic Exposure
Principles and Practice, Davis Co, Philadelphia (1995), pp. 92-96
View Record in ScopusGoogle Scholar
7.
DN Chesney, MO Chesney
Radiographic Photography
(3rd edn.), Blackwell Scientific Publications, Oxford (1971), p. 293
View Record in ScopusGoogle Scholar
« Last Edit: February 02, 2022, 08:16:57 pm by LaserSteve »
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Offline CwazyWabbit

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #72 on: February 10, 2022, 02:15:51 pm »
Found this info on the serial protocol being used, not sure if it adds any more to what you already know though.
 
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Offline Andrew Seltzman

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #73 on: February 23, 2022, 02:33:22 pm »
@danielbriggs

I wrote a MATLAB package for cone beam CT on the DX-50, it should run the MX-20 since it uses the same protocol.
http://www.rtftechnologies.org/physics/faxitron-DX50-CT-scan.html
 
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Offline danielbriggs

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Re: Faxitron MX-20 Reverse engineering (with some good results)
« Reply #74 on: February 24, 2022, 10:00:42 pm »
Thank you Andrew! Really impressive work.  :-+
What an excellent resource on your site. I'll work my way through the videos, and adapt any code where appropriate for my MX-20.
 


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