M. N. Mazziotta(LAT-TD-01128)

TKR trigger simulation (timing study)

Udine, January 30-31, 2003

Aim of this workRequirements for the hardware design:

1. Trigger delay to latch the discriminator output

2. Trigger efficiency vs threshold and coincidence window

3. Hit capture efficiency vs delay and threshold

Applications:

1. Detector acceptance calculation

2. GRB time detection

3. ....

Simulation code

GEANT 3.21: geometric description and tracking

• 4 middle trays (4 x-z layers and 4 y-z layers)

HEED: Si energy loss and e-h pairs production

• Front end electronics simulation (transfer function)

• Induced current calculation (Ramo’s Theorem)

Timing studies

The threshold value has been set at a fraction of Vmip.

Volt

ag

e

time

Vth

T1 T2

TOT

Trigger timingTrigger: 6-fold coincidence of the first 3 x-z and 3 y-z fired planes

Coincidence window = 1 s (one shot)

Tc (time coincidence) = the last T1 of the triggered planes

Tf (trigger falling edge) = the first T2 of the triggered planes

Time coincidence width = Tf-Tc

T1

T1

T1

T2

T2

T2Tc Tf

Trigger timing

Timing studies: 1 GeV muons

Strip signals:

Vth=1/4Vmip

Timing studies: 1 GeV muons

Plane

signals:

OR of the strips in the

plane

Timing studies: 1 GeV

Two peaks!

Plane

signals:

OR of the strips in the

plane

Trigger timing: 1 GeV muons

Trigger timing: 1 GeV

Hit capture efficiency T2-Tc = time interval when the strip signal is over the threshold (respect to the trigger time Tc).

Td = time interval between the trigger and the hit capture time (delay)

The hit is “captured” if Td < T2-Tc

The efficiency as a function of Td is evaluated from the cumulative distribution of T2-Tc

1 GeV muons have been simulated at zenith angles 0º, 10º,20º,30º,40º and uniformly distributed in azimuth

Hit capture efficiency: 1 GeVTrig to TKR

Tc

Hit capture efficiency: 1 GeV =40°, =0° Trig to TKR

Tc

Hit capture efficiency: 1 GeV =0°: threshold scanning

Trig to TKR

Tc

Hit capture efficiency: 1 GeV =40º:threshold scanningTrig to TKR

Tc

Future plansGLEAM

HIT (rin, rout, E)

DIGIT

(fired strips, ToT per layer)

GLAST DIGI

TkrTrigTiming

analysisL1T

Preliminary results (2 GeV , =0°)

Plane

signals:

OR of the strips in the

plane

Preliminary results (2 GeV , =0°)

Preliminary results (2 GeV , =0°)

Trig to TKR

ConclusionsA trigger timing study has been performed on

a mini TKR tower consisting of 4 middle trays The trigger hit capture efficiency has been

also evaluated

To evaluate the trigger efficiency a simulation on the whole TKR system is needed: GLEAM era!

(people: M.N.M., M. B., F. L., F. G., N. G.)