[ Identification | Description | Input parameters | Links ]
ESS_moderator_short ComponentProduces a time-of-flight spectrum, from the ESS parameters Chooses evenly in lambda, exponentially decaying in time . Adapted from Moderator by: KN, M.Hagen, August 1998 Units of flux: n/cm^2/s/AA/ster (McStas units are in general neutrons/second) Example general parameters (general): size=0.12 Lmin=0.1 Lmax=10 dist=2 focus_xw=0.06 yh=0.12 nu=50 branchframe=0.5 Example moderator specific parameters (From F. Mezei, "ESS reference moderator characteristics for ...", 4/12/00: Defining the normalised Maxwelian M(lam,T) = 2 a^2 lam^-5 exp(-a/lam^2); a=949/T; lam in AA; T in K, and the normalised pulse shape function F(t,tau,n) = ( exp(-t/tau) - exp(-nt/tau) ) n/(n-1)/tau, the flux distribution is given as Phi(t,lam) = I0 M(lam,T) F(t,tau,n) + I2/(1+exp(chi2 lam-2.2))/lam*F(t,tau2*lam,n2) ) a1: Ambient H20, short pulse, decoupled poisoned T=325 tau=22e-6 tau1=0 tau2=7e-6 n=5 n2=5 chi2=2.5 I0=9e10 I2=4.6e10 branch1=0 branch2=0.5 a2: Ambient H20, short pulse, decoupled un-poisoned T=325 tau=35e-6 tau1=0 tau2=12e-6 n=5 n2=5 chi2=2.5 I0=1.8e11 I2=9.2e10 branch1=0 branch2=0.5 a3: Ambient H20, short pulse, coupled T=325 tau=80e-6 tau1=400e-6 tau2=12e-6 n=20 n2=5 chi2=2.5 I0=4.5e11 I2=9.2e10 branch1=0.5 branch2=0.5 b1: Liquid H2, short pulse, decoupled poisoned T=50 tau=49e-6 tau1=0 tau2=7e-6 n=5 n2=5 chi2=0.9 I0=2.7e10 I2=4.6e10 branch1=0 branch2=0.5 b2: Liquid H2, short pulse, decoupled un-poisoned T=50 tau=78e-6 tau1=0 tau2=12e-6 n=5 n2=5 chi2=0.9 I0=5.4e10 I2=9.2e10 branch1=0 branch2=0.5 b3: Liquid H2, short pulse, coupled T=50 tau=287e-6 tau1=0 tau2=12e-6 n=20 n2=5 chi2=0.9 I0=2.3e11 I2=9.2e10 branch1=0 branch2=0.5
| Name | Unit | Description | Default | |
| size | m | Edge of cube shaped source | ||
| Lmin | AA | Lower edge of wavelength distribution | ||
| Lmax | AA | Upper edge of wavelength distribution | ||
| dist | m | Distance from source to focusing rectangle; at (0,0,dist) | ||
| focus_xw | m | Width of focusing rectangle | ||
| focus_yh | m | Height of focusing rectangle | ||
| nu | Hz | Frequency of pulses | 50 | |
| T | K | Temperature of source | 325 | |
| tau | s | long time decay constant for pulse, 1a | 22e-6 | |
| tau1 | s | long time decay constant for pulse, 1b (only for coupled water, else 0) | 0 | |
| tau2 | s/AA | long time decay constant for pulse, 2 | 7e-6 | |
| n | 1 | pulse shape parameter 1 | 5 | |
| n2 | 1 | pulse shape parameter 2 | 5 | |
| chi2 | 1/AA | lambda-distribution parameter in pulse 2 | 2.5 | |
| I0 | flux | integrated flux 1 (in flux units, see above) (default 9e10) | 9e10 | |
| I2 | flux*AA | integrated flux 2 (default 4.6e10) | 4.6e10 | |
| branch1 | 1 | limit for switching between distribution 1 and 2. (has effect only for coupled water, tau1>0) | 0 | |
| branch2 | 1 | limit for switching between distribution 1 and 2. (default value 0.5) | 0.5 | |
| branchframe | 1 | limit for switching between 1st and 2nd pulse (if only one pulse wanted: 1) | 0 | |
| target_index | 1 | relative index of component to focus at, e.g. next is +1 this is used to compute 'dist' automatically. | +1 |
| AT ( | , | , | ) RELATIVE | |||
|---|---|---|---|---|---|---|
| ROTATED ( | , | , | ) RELATIVE |
ESS_moderator_short.comp.
[ Identification | Description | Input parameters | Links ]
Generated on 2023-09-19 20:01:36