**From:** Mario Santana Leitner (*Mario.Santana@cern.ch*)

**Date:** Tue Mar 20 2007 - 01:19:46 CET

**Previous message:**Sebastien WURTH: "Re: Is there a maximum number of energy bins in USRTRACK card ?"**In reply to:**hamide jalali: "questions with source & USRBIN"**Next in thread:**Giuseppe Battistoni: "Re: questions with source & USRBIN"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ] [ attachment ]

Hello

Concerning the first question, from the source file that you attach, I can't see where you do the random generation within the sphere, you seem to use the 6 coordinates of the beam:

TXFLK (NPFLKA) = UBEAM

TYFLK (NPFLKA) = VBEAM

TZFLK (NPFLKA) = WBEAM

* TZFLK (NPFLKA) = SQRT ( ONEONE - TXFLK (NPFLKA)**2

* & - TYFLK (NPFLKA)**2 )

* Polarization cosines:

TXPOL (NPFLKA) = -TWOTWO

TYPOL (NPFLKA) = +ZERZER

TZPOL (NPFLKA) = +ZERZER

* Particle coordinates

XBEAM = 0.D0

YBEAM = 0.D0

ZBEAM = 8.D2

XFLK (NPFLKA) = XBEAM

YFLK (NPFLKA) = YBEAM

ZFLK (NPFLKA) = ZBEAM

---------------------------------

I would suggest doing something like this, in the input file, you use the BEAMPOS card as follows:

WHAT(1)-WHAT(3):x,y,z coordinates of the center of the sphere (XBEAM-ZBEAM)

WHAT(4): radius of the sphere (UBEAM)

If you want to generate in the VOLUME of the sphere:

r = UBEAM * (FLRNDM(dummy) ** (ONETHI))

alpha = PIPIPI * (FLRNDM(dummy))

beta = TWOPIP * (FLRNDM(dummy))

If you would want to generate only in the surface of the sphere, you would use something like this instead:

r = UBEAM

alpha = ACOS (ONEONE - TWOTWO * FLRNDM(dummy))

beta = TWOPIP * (FLRNDM(dummy))

In any case,

XFLK (NPFLKA) = XBEAM + r * SIN(alpha) * COS(beta)

YFLK (NPFLKA) = YBEAM + r * SIN(alpha) * SIN(beta)

ZFLK (NPFLKA) = ZBEAM + r * COS(alpha)

If the particles are pointing the center of the sphere, as you wrote, then:

TXFLK (NPFLKA) = -SIN(alpha) * COS(beta)

TZFLK (NPFLKA) = -COS(alpha)

TYFLK (NPFLKA) = SQRT ( ONEONE - TXFLK (NPFLKA)**2

& - TZFLK (NPFLKA)**2 )

Hope this helps,

Mario

**Previous message:**Sebastien WURTH: "Re: Is there a maximum number of energy bins in USRTRACK card ?"**In reply to:**hamide jalali: "questions with source & USRBIN"**Next in thread:**Giuseppe Battistoni: "Re: questions with source & USRBIN"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ] [ attachment ]

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