This modernized edition of the charged particle Monte Carlo ray-tracing computer program TURTLE
(Trace Unlimited Rays Through Lumped
Elements, deducted from Transport) consists in principle of the former
CERN/SLAC/FERMILAB version of Decay Turtle coded in portable FORTRAN-77 [1] and C for the
OS-dependant system calls. But
many new features have been added [2]. The most important one is the inclusion
of multiple scattering and absorption of charged particles in matter, which
makes it possible to forecast losses of protons (or mesons) in beam lines
furnished with collimators, slits and splitter
strips and wires to a relative accuracy in the part per million range
(important for designing high intensity/low loss proton beam lines or low
electron-background µ-meson beam lines). For this purpose some code
fragments have been extracted from the computer code REVMOC [3], which has been
developed at TRIUMF. This enriched and improved Turtle FORTRAN code has also
been embedded in a new shell written in C++
(see Fig.1, 51 kB)
(or Tcl/Tk + csh for x86-Linux and Mac OS X - X11
(see Fig.2, 50 kB)) and is providing
some pretty and handy GUI type tools (e.g. 1 [for x86-Linux and Mac OS X - X11] or 2 [for Windows]
graphic histogram option[s]), which make it easier to run Turtle and to interpret the results.
It should be mentioned here, that the usage of this program was responsible for the
successful design of the proton beam line to the SINQ
(low looses in the beam cellar) and the reduction and containment of the losses after the
electrostatic high-energy beam splitter (EHT). In order
to get a list of the currently available most important features of the Graphic Turtle Framework
(in comparison with the Graphic Transport Framework), please click
here. A short résumé
about the usefulness of the Graphic Turtle Framework (together with Transport and MENT) has been published in the
PSI Scientific and Technical Report 2000 Volume VI (Large Research Facilities) on
pages 24 & 25. A whole collection of
Turtle input files
from different users is available for inspection and/or downloading.
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To keep the Graphic Turtle Framework in good shape some modifications and bug fixes are sometimes necessary. So -
from time to time - watch out for modifications and new
features.
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Before running Turtle it is recommended to run Transport in order
to design the optics of your beam line in first and eventually in second order. This is
achieved mainly with the great fitting capabilities of Transport. Afterwards only a few
lines of the Transport input file have to be modified for being used by Turtle.
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If you prefer to run the Windows versions of the Graphic Turtle and Transport Frameworks under x86-Linux, then
you may do this today by installing the
VMware for some x86-Linux Systems. After configuration and licensing of VMware and the
installation of one of the 32-bit Windows operating systems inside this virtual machine for
x86-Linux, you may then download and install the Windows versions of Turtle and/or Transport and
run these programs under Windows while x86-Linux is up.
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If you prefer to run the Windows versions of Turtle and Transport on an Apple Computer, then you may
do this today by installing the
Virtual PC 6.1 for Mac OS X. After installation and licensing of Virtual PC and the
installation of one of the 32-bit Windows operating systems inside this virtual machine for
the Mac, you may then download and install the Windows versions of Turtle and/or Transport and
run these programs under Windows while Mac OS X is up.
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In order to give an other demonstration of the capabilities of Turtle, an
example from the medical field of 'treatment of ocular tumors'(or from the field of
'terrestrial testing of radiation hardness of electronic spacecraft components') is also presented
here.
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The usefulness of Graphic Turtle for even large acceptance secondary beam lines was demonstrated for the case of
the new µE4 muon beam line at PSI.
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A hint for users with a Desktop-PC running under Windows XP Professional (SP2) and a motherboard having an Intel FSB-533 or 800
chipset (e.g. ASUS P4PE and a 3.06 GHz Pentium-4 processor) supporting Intel's new Hyper-Threading Technology:
If you start the Graphic Turtle Framework twice and run from each one the DLL with an input file (FOR001.DAT) containing the line 16. 190. 2. 100. /Meta/ ;
then the results of the 2 equivalent runs (threads) are accumulated and you will gain a time-factor around 1.3 (for the same amount
of totally tracked particles) because of this new technology. Thus, for dual-threaded Monte-Carlo computations the
3.06 GHz Pentium-4 behaves like a 4 GHz CPU (actually like a Dual-P4 with two 2 GHz CPUs) with ~0.7 Giga-Flops !
If you are using a modern x86-Linux version (with a SMP-Kernel 2.4.x, x>=21 or 2.6.x) on the same hardware platform, then you will
experience an equivalent speed gain with 'Turtle for x86-Linux' when running 2 threads concurrently.
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If you have a PC with an AMD Athlon-64 processor and one of the new x86_64 Linux systems
(Fedora Core 2 or SuSE 9.1) installed on it, then you may use the 64-bit version of Turtle
(download and install the file turlin64.tgz instead of turlinux.tgz). The gain of computation
speed of the 64-bit verson of Turtle over the 32-bit version is a factor of 2.0-2.5
(depending on used beam line elements and parameters like with or without required higher
order contributions).
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A bootable live CD (see screen shot of the booted system)
has been created which contains among many other preinstalled programs
'Turtle for Windows' and 'Turtle for Cygwin'. (Cygwin is a UNIX/Linux-like OS
running on top of Windows.) It may be downloaded as iso-file (
U_R_live_CD.iso, 655 MB,
instructions at
1-readme.txt). With low-speed internet connections you may download the
split images.
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This version of Turtle maintained by Urs Rohrer is freely available and distributable with one restriction:
If you use it for some work whose results are made public in a report or a journal publication,
then in a gentlemen's agreement you have to reference it properly like: PSI Graphic Turtle Framework by U. Rohrer based
on a CERN-SLAC-FERMILAB version by K.L. Brown et al. A reference like: Turtle by K.L.
Brown et al. is considered as inappropriate, because more than half of this framework's code
has not been produced by K.L. Brown et al. (See: Compendium of Turtle Enhancements and
Modifications and new features.) Nevertheless, I appreciate very much the excellent work
done by K.L. Brown et al. and all the others, who have contributed to the content of the present
version. (See also the references at the end of the Compendium.)
Notice:
PSI and the author of this program do not
guarantee the accuracy and/or usefulness
of the results achieved with this program.
The output of it is strongly dependent on
the given input and therefore the confirmation
of the correctness of all the results is the
responsibility of the user.
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References:
[1] K.L. Brown, Ch. Iselin, D.C. Carey: Decay Turtle, CERN 74-2 (1974)
[2] Urs Rohrer: Compendium of Decay Turtle Enhancements,
Show text (60 kB)
[3] C. Kost, P. Reeve: REVMOC - A Monte Carlo Beam Transport Program,
TRI-DN-82-28 (1983).
Last updated by
Urs Rohrer on 20-April-2007
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