CPM to DPM

[Eugene]

Help I know that I'm old, If I use a 3030 and count a bkg of 7 for 10 mins, and then a smear that is 2 cpm and I counted it for .5 mins and my eff is 5.98 What is my DPM

[Rennhack]

Help I know that I'm old, If I use a 3030 and count a bkg of 7 for 10 mins, and then a smear that is 2 cpm and I counted it for .5 mins and my eff is 5.98 What is my DPM

A few things here.... A Ludlum 3030 is a 'counter' and not a probe.  The meter just counts the clicks, and has nothing to do with the efficiency.  I'm not sure why you provided that information.  The probe it is typically pared with is the Model 43-10-1, which has an efficiency of (4pi): 37% for 239Pu; 32% for 230Th; 39% for 238U; 5% for 14C; 27% for 99Tc; 29% for 137Cs; 26% for 99Sr/90Y.  I'm just saying your 6% efficiency looks odd.

I really doubt you are using it for C-14, especially with your background. I have to say, 6% efficient is terrible, even for alpha.  Understand there is a difference between 4 pi and 2 pi geometry/efficiency, so those numbers listed above don't relate directly.... and you didn't come here looking to learn geometry.

On to your question

Your background is 0.7 cpm  (7/10)

Is your smear 2 cpm or 2 counts in 30 seconds?

If it is 2 cpm, then why are you telling me how long you counted it for (unless you want to know the MDC/MDA).

2 cpm - 0.7 cpm is 1.3 cpm net counts

1.3 cpm divided by the efficiency.... is approximately 22 dpm.

IF it is 2 counts for 30 seconds, and not 2 cpm... then it is 4 cpm - 0.7 cpm = 3.3 net cpm divided by 0.0598 = 55 dpm

Old has nothing to do with basic fundamentals. 

DPM = ( CPM - BKG ) / EFF

I would highly recommend you follow the link below, and buy the two books on the left side of the page (NOT the cram notes):

http://www.westrain.org/

[Eugene]

sorry for the question, and Yes I did buy the book's Thanks When I run the info I got 22 dpm/cm2 also just questioned the answer. now what would it me with a 2360 bkg 2 mins getting 2 cpm and 30 sec count time and I get 10 cpm A.
Eugene

[Rennhack]

sorry for the question, and Yes I did buy the book's Thanks When I run the info I got 22 dpm/cm2 also just questioned the answer. now what would it me with a 2360 bkg 2 mins getting 2 cpm and 30 sec count time and I get 10 cpm A.

Here is your answer:

DPM = ( CPM - BKG ) / EFF

2360... I assume you mean the instrument is a Ludlum 2360 scaler/data logger.  Again, that has nothing to do with the question.  The probe is the only thing that matters... and that's only if you are trying to figure out for yourself what the probes efficiency is (which you are not).  Compatible Detectors: 3-1-1, 43-2-2, 43-20, 43-68, 43-89 and 43-93. With the 43-89 being the most popular.

Again, it doesn't matter how long the background or sample count time is, if the result is already in CPM.

And lastly, you didn't tell me the efficiency.

DPM = ( CPM - BKG ) / EFF

DPM = ( 10 - 2 ) / EFF
DPM = ( 8 ) / EFF

If you were to use a generic 10% efficiency as an example, then the answer would be 8 / 10% = 80.

Please don't ask the same question a third time, that will tell me that you aren't trying to learn, you just want an answer.  And I don't have time to do your work for you.  I will help you learn, but you didn't appear to learn from the first question, because you asked the same basic question again.

Secondly, IF you did actual get a copy of  the RCT Fundamentals, then I would suggest you spend more time with it.

Instead of asking for an answer, perhaps you could explain what part of the equation you don't understand, and we can help you with understanding the equation. OR... you can post what you think the answer is (showing your work), and ask if that is correct.

For these questions, the model number of the instrument is irrelevant.  It is what is known as a 'distractor'.  Just like the count time, if they have already given you the measurement in CPM.

If they say the instrument reads 10 total counts for a sample, and you counted the sample for 2 min, then that would be 10 counts per 2 min, or 10/2 =  5 counts per min, or 5 CPM.

Same thing with the background, it is just the CPM of the background.  You subtract the CPM of the background from the CPM of the sample, to get your "Net CPM".

Once you calculate your Net CPM, you divide that by the efficiency to convert the CPM into DPM.

[GLW]

Here is your answer:

remember marssim's maxim #3:

avoid answering technical on forums and blogs,...

marssim's maxim #4:

avoid acquiring tech answers on forums and blogs,...

I could go on illustrating all the reasons,...

but it should be obvious,...        

[hamsamich]

if it was a really strange question then cool, but this one aint one of those.  I like head scratchers.

[SloGlo]

eugene, aye yam thinking yore knot sew auld as lazy. yins gaught you're answer da 1st thyme compleat wit formulation n reference material witch yue sayed yew awl ready bot.
sew wye the 2nd query, two sea iffen they're was a moor fast weigh too the answer?

[GLW]

eugene, aye yam thinking yore knot sew auld as lazy. yins gaught you're answer da 1st thyme compleat wit formulation n reference material witch yue sayed yew awl ready bot.......

marssim's maxim #3

....sew wye the 2nd query, two sea iffen they're was a moor fast weigh too the answer?

marssim's maxim #4

.....now what would it me with a 2360 bkg 2 mins getting 2 cpm and 30 sec count time and I get 10 cpm A....

GLW's corollary to marssim's maxim #4:

if you need to defend a technical analysis conclusion from advice obtained at an internet forum, well,... good luck with that,...

[Rennhack]

remember marssim's maxim #3:
avoid answering technical on forums and blogs,...

This site is here to help people.  I am happy to happy to help others.  These questions are simple and straight forward, as apposed to some we have gotten, ie. "If I want to surrogate a hard to detect alpha emitter to a soft beta, and my DCGLw is xyz, what setting do I use for Resrad for a farm scenario?" (I may have merged 2 or 3 there).

I can answer them for the same reason that I probably sounded too harsh when I answered them (and for that, I am sorry).  It's a simple, straight forward question, with an easy, straight forward answer.

Reminds me of the time a technician of mine who wanted to be a CHP asked what the formula was to 'make' 50 microR/hr gamma to mRem/hr

I was young and single back then.... and was probably less then kind when I explained that there was no 'formula', that it was a conversion, you just move a decimal point, like 50/1000.

But now I am old and married for 13+ years, and have kids.  I am more patient and understanding. -- But apparently I still need to work on it.

[GLW]

This site is here to help people.....

yes, it is,...

e.g., cpm/dpm/etc.,...

https://www.nukeworker.com/forum/index.php/topic,8457.msg58324.html#msg58324

https://www.nukeworker.com/forum/index.php/topic,33648.msg184369.html#msg184369

https://www.nukeworker.com/forum/index.php/topic,34705.msg161927.html#msg161927

https://www.nukeworker.com/forum/index.php/topic,21194.msg110097.html#msg110097

https://www.nukeworker.com/forum/index.php/topic,11132.msg60555.html#msg60555

https://www.nukeworker.com/forum/index.php/topic,3145.msg23698.html#msg23698

and that's just a 2 minute, single parameter search,....

we have done this before, technical is best handled by PM where assumptions, parameters, etcetera can be asked for in detail without a multi-day, multi-post back and forth that not only loses the casual observer but then invites everyone's "what if" interjections ala that other net den aka rad,....safe?!?!?!?

I would posit the first response (aka Reply #1) was sufficient for any "technician" who can sit for and pass a DOE core or NUF battery,....

after "Reply #2" the thread reads akin to "My steering wheel shimmies when I push the brake pedal, my mechanic said I should get the front suspension and the front brakes checked and corrected as needed, but I'm sure it's in the transmission, what can you give me to take back to my mechanic that will prove the shimmy comes from the transmission"?

now,....there have been two or three phenomenal technical threads on these forums over the last dozen years plus,...

those threads were contributed to by seasoned, licensed, ROs, SROs, SMEs & SMs,...

others by seasoned, certified technicians, radengs, etcetera,...

not so much basement bound CR Specialist wannabes,....

I'm just saying,....

but, for the eternally optimistic and stooge suffering users and posters,....have at it and enjoy the day,.....

[Nuclear NASCAR]

after "Reply #2" the thread reads akin to "My steering wheel shimmies when I push the brake pedal, my mechanic said I should get the front suspension and the front brakes checked and corrected as needed, but I'm sure it's in the transmission, what can you give me to take back to my mechanic that will prove the shimmy comes from the transmission"?

Finally, something I can relate to being a formerly paid mechanic....(there are no ex-mechanics, just those who get paid or don't get paid for their labors)

[SloGlo]

marssim's maxim #3

marssim's maxim #4

GLW's corollary to marssim's maxim #4:

if you need to defend a technical analysis conclusion from advice obtained at an internet forum, well,... good luck with that,...

know argument wit any thing their.