RE: How to Calculate Electronic Damage?

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Tue, 22 Jan 2013 02:38:09 -0800 (PST)

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I would like to stress a misunderstanding that I think I notice in
what Vahan Petrosyan writes (and in what is being said to me privately by
several people).
There are several quantities (dose, NIEL, high-energy hadron fluence,
silicon-1MeV-neutron-equivalent fluence, DPA, etc.) that are known to be
CORRELATED to various types of radiation damage.
FLUKA allows to calculate those quantities, but does not calculate the
radiation damage.
The type of correlation can be of different kinds, and in simplest cases
is just a proportionality. But even in the simplest cases the proportionality
factor is not known, or is known to change with the radiation field or with
different industrial batches of the same material. The only way to find it
out is a calibration: given a certain material, expose it to a certain
radiation field, calculate the damage quantity of interest with FLUKA and
submit the material to quantitative damage tests.

This is very similar to what happens with the biological effects of radiation.
There are some quantities (dose, dose equivalent) that are known to be
correlated to the probability of harmful effects in human beings (e.g.
the development of cancers). FLUKA can well calculate dose and dose equivalent,
but not the probability of developing a cancer. The "calibration factor"
to convert dose and dose equivalent to cancer probability depends on
many parameters (age, sex, type of radiation, etc.) and is obtained
by epidemiological studies.

So, please do not ask "how to calculate damage", in the same way as you
don't ask "how to calculate cancers".


On Tue, 22 Jan 2013, Anton Lechner wrote:

> Dear Vahan,
> In principle, you correctly implemented the USRBIN scorings for dose,
> Si-1MeV neutron-equivalent and high-energy hadron fluence (ie. hadrons with
> energies >20 MeV). However, considering that your primaries are 20 MeV
> electrons, not all scorings make sense.
> For example, high-energy hadron fluence is relevant if one is interested in
> single event effects, which are of stochastic nature. In your particular
> case, the HADGT20M-based scoring is irrelevant as no high-energy hadrons are
> produced.
> On the other hand, cumulative damage can be due to the deposited dose (note
> that DOSE scoring is actually the total dose and not the total ionizing
> dose, but the difference is minor in most cases, also in your application)
> as well as due to atom displacement. The latter is related to the
> non-ionizing energy loss (NIEL) and in case of silicon, displacement damage
> is often described in terms of 1 MeV neutron-equivalent fluence (SI1MEVNE).
> It should be emphasized that the fluence conversion coefficients used in
> SI1MEVNE are based on silicon data and hence, if you are interested in
> damage to other materials, you might want to consider NIEL directly (it is
> also possible to score NIEL in FLUKA).
> At this point it really depends on what what you are actually interested in.
> Radiation-induced damage can range from surface damage (e.g. charge
> accumulation at insulation layers due to ionizing energy loss) to bulk
> damage (e.g. change of the doping concentration).
> Also note, that the approximative correlation between dose and 1 MeV
> neutron-equivalent fluence shown in the attached picture only holds for a
> certain radiation environment, and will likely be different in your case.
> More specifically, the graph applies for space/high-altiude environment (and
> is shown as such in the course to give an example).
> Cheers
> ____________________________________________________________________________
> From: [] on
> behalf of vahan petrosyan []
> Sent: 07 January 2013 10:29
> To:
> Subject: How to Calculate Electronic Damage?
> Hi I am trying calculate electronic damage when 20 Mev (or greater )
> electron beam hits a sample target (Silicon).
> I carefully red the article and tried to implement it myself.
> age2Electronics.ppt
> Now I have couple of SIMPLE questions regarding to that
> As I understood in order to calculate damages I should do following steps
> 1) Do calculation USERBIN and USERTRACK cards with part. type Dose,
> 2) Take values from plots of that cards
> 3) Compare plots values with the chart that I attached ( See Attached
> Image)
> I ask experts If you have time can you take a look to my input card and say
> what I may miss?
> Many Thanks!
Received on Tue Jan 22 2013 - 12:33:01 CET

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