Thank you very much for Alberto and Felix Horst' comments. I get a lot of benefits from them.
Best regards
Bo Yang
-----邮件原件-----
发件人: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-discuss_at_mi.infn.it] 代表 Alberto Fasso
发送时间: 2015年3月18日 18:27
收件人: fluka-discuss_at_fluka.org
抄送: 杨博
主题: Re: [fluka-discuss]: how to define a thick target bremsstrahlung
Dear Bo Yang,
"thick target bremsstrahlung" has no precise physical meaning. Its definition is arbitrary: everybody can give a different definition, depending on the application.
For instance, Ervin B. Podgorsak, in his book "Radiation Physics for Medical Physicists" gives still another definition (on p. 164):
"Thick x-ray targets have thicknesses of the order of the range of electrons R in the target material. In practice, typical thicknesses are equal to about 1.1 R to satisfy two opposite conditions:
1. To ensure that no electrons that strike the target can traverse the target 2. To minimize the attenuation of the bremsstrahlung beam in the target"
Since your application is radiation protection, you should adopt the most conservative definition, which seems to be that of IAEA188.
Alberto
On Wed, 18 Mar 2015, 杨博 wrote:
>
> Dear Fluka user
>
> Rencently ,I have been working on radiation protection of X-ray
> generated by high-intensity laser facility. The source term is
> high-energy electrons following Maxwell distribution whose averaged
> energy is from a few MeV to Hundreds of MeV for different laser
> intensities . I would like to calculated the bremsstrahlung yield
> generated by these high-energy electrons hiting high-z thick target
> and evaluate this kind of ionizing hazard to compare with that of
> conventional electron accelerator. But I found a disagreement about
> the discription of thick-target bremsstrahlung between IAEA188 and
> NCRP 144. IAEA188 define the thick-target bremsstrahlung as a target
> of thickness corresponding to the maximum radiation called “optimum
> target”,But NCRP144 define the thick-target bremsstrahlung as a target
> that is sufficiently thick to allow full development of the
> electro-magnetic cascade. I believe that these two kind of targets are
> not the same one and the bremsstrahlung yield from the former is much larger than that from the later.
>
> So I am very confused about the thick-target bremsstrahlung yield and
> tenth values in different materials from IAEA188 and lately adopted by NCRP 144.
>
> I don"t know why the definition of thick-target bremsstrahlung is
> different，but the results can be shared by IAEA and NCRP and how
> should I define the thick target in the simulation in terms of
> conservative practice.I hope you could help me to solve it.
>
> Thanks in advance
>
> Best regard
>
> Bo Yang
>
>
>
>
>
>
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Received on Fri Mar 20 2015 - 07:52:43 CET