Alignment for 2010 run and n_TOF 2009 beam profile M. Calviani (CERN), S. Andriamonje (CERN), E. Berthoumieux (CEA), C. Guerrero (CIEMAT),

Outline 23 September 2010M. Calviani - n_TOF Analysis Meeting CERN2 Alignment campaign review for 2009 and 2010, summary of activities Activities in 2010 Update on the experimental beam profile RESULTS AS OF APRIL 2010 (n_TOF Collaboration Board 04/2010)  Complete set of analysis routine now freely available /afs/cern.ch/exp/ntof/XYMG  Analysis now responsibility of CEA

Introduction – summary of 2009 observations 23 September 20103M. Calviani - n_TOF Analysis Meeting CERN Measured neutron fluence during the 2009 run was ~20% less than expected (comparison with simulations and old official fluence) n_TOF experimental beam profile  misalignment of the 2 nd collimator 11% of fluence recovered in November 2009  tilt of ~2 mm of 2 nd collimator (-8 mm upstr., -6 mm downstr.)! -9, -4 = -5 mm 0, -4 = +4 mm -4, -4 = 0 mm -8, -4 = -4 mm -7, -4 = -3 mm -6, -4 = -2 mm In 2010 the alignment has been performed by looking at the spallation target 5 cm left radially (looking at target) to intercept the maximum of the fluence NB: the theoretical beam line (with which the 2 nd collimator is aligned) has been defined by looking at the 1 st collimator center

Alignment campaign September 2010M. Calviani - n_TOF Analysis Meeting CERN4 Surveyor’s theoretical beam line defined with the following steps: 1. A theodolite is placed in the Escape Lane (FIC2 place), where fixed (2001) reference points are placed in the floor 2. Theodolite view is set to 0.67 ° proper inclination of the TOF line. For the radial direction, uses a reference in the EL 3. Observation: The center of the theodolite is very close to the mechanical center of the neutron window 1.Vertical ok 2.Horizontal is shifted by ~1 cm

Alignment campaign September 2010M. Calviani - n_TOF Analysis Meeting CERN5 The 1 st collimator is shifted up by 1.9 cm, left by 0.75 cm, looking to the target No information on the possible tilt Explains the 2009 movements on the 2 nd collimator ~9% decrease in fluence from the simulations Movement possible but not easy (not foreseen for now) NB: this shift was always in place, since the construction of the facility! 2010 Alignment will be performed by looking: Vertically  mechanical center of the window Radially  5 cm to the left of the mechanical center New reference points will be established in the EAR-WS

2010 plans on alignment 23 September 2010 M. Calviani - n_TOF Analysis Meeting CERN6 1. First measurements included the movement of the 2 nd collimator to try maximizing the fluence vertical movement only horizontal movement available but too risky for the moment (possible if beam profile show a significant horizontal skew) 2. SiMon + XYMG with 10 B or 235 U sample simultaneous profile and fluence variation evaluation borated water (*)  CEA data 235 U will allow to have a reasonable statistics in the HE part XYMG current routine (v. 2.8/2.9) limited by a significant dead-time (signal is ~200  s long) X-Y MicroMegas Silicon Monitor Monitoring MGAS

X-Y MicroMegas for n_TOF (1/2) M. Calviani - n_TOF Analysis Meeting CERN7  Detector based on the “bulk” technique  Active region is separated in two active regions: conversion (drift)  480 V amplification (mesh) gap  330 V  Anode segmented into 106 strips for each X and Y pad (tilted 90 deg.) Application for monitoring of the n_TOF neutron beam Neutron beam profile from thermal up to ~1 MeV Detector used for helping in the alignment of the experimental area experimental (almost real-time) position of the neutron beam 23 September 2010 n_TOF Collaboration Meeting 2009

X-Y MicroMegas for n_TOF (2/2) M. Calviani - n_TOF Analysis Meeting CERN8 Neutron converter, enriched 10 B 4 C, deposited by sputtering on a 3 cm radius on a coppered (1  m) kapton (12.5  m) substrate. thin ~ 24 nm thickness (no dead-time) thick ~ 2  m thickness (for the high energy part)  60 mm x 60 mm with 106 strips per pad  566  m pitch  212 channels too much for fADC  two multiplexer card based on Gassiplex concept have been used  2 output directly to the n_TOF fADC  Trigger signal is available through the mesh signal  n_TOF available Gassiplex is able to read only 96 strips (reduced active area)  DAQ and analysis routine have been specially developed Operation principle: Read consecutively all the X and Y strips 2  s per strip  total of ~192  s dead-time issues if the count rate is too high (but non-paralyzable) 23 September 2010 n_TOF Collaboration Meeting 2009

X-Y MicroMegas Analysis procedure (1/2) M. Calviani - n_TOF Analysis Meeting CERN9 Digitized Gassiplex signals are the input of the analysis Each mesh signal trigger the aperture of a gate of 192  s wide (T/H) In order to record MeV neutrons, the prompt flash is remove “by hardware” in the Gassiplex trigger stage 192  s Pedestal runs are needed to evaluate mean value of the signal is each of the strips + level shift Amplitude distribution of signals after pedestal subtraction and level shift correction (+/- 2 channels baseline) 23 September 2010 n_TOF Collaboration Meeting 2009

X-Y MicroMegas Analysis procedure (2/2) M. Calviani - n_TOF Analysis Meeting CERN10 Cluster analysis used to search for strips that have fired above the mean value of baseline (> 10 ch above baseline with >= 1 fired strip) “Center-of -charge” applied to define the interaction point Coincidence method to reconstruct a 2D image of neutron beam # fired strips >1 rotation of 225 deg. to obtain image as of neutron beam energy selection based on TOF 23 September 2010 n_TOF Collaboration Meeting 2009

X-Y MicroMegas 2009 results up to 1 keV M. Calviani - n_TOF Analysis Meeting CERN11 Assumed tilt is in agreement to what has been found during the 2 nd collimator alignment tests Fit on data performed on the base of a gaussian + step function th. - 1 eV 1 eV – 1 keV Simulation assuming perfect alignment Simulations assuming -2 mm tilt upstream 2 nd collimator th. - 1 eV 1 eV – 1 keV 23 September 2010

Updates on the experimental beam profile 2009 with XYMG  100 keV – 1 MeV 23 September 2010M. Calviani - n_TOF Analysis Meeting CERN12 Horizontal Vertical

X-Y MicroMegas 2010 results 23 September 2010M. Calviani - n_TOF Analysis Meeting CERN13 Beam profile run : Main observations: beam profile seems to be symmetric  effectiveness of 2 nd collimator alignment data at higher energy mainly limited by statistics (with analysis routine v2.9 (the latest by MC))  improved by updates by CEA

Analysis routines 23 September 2010M. Calviani - n_TOF Analysis Meeting CERN14 1. Freely available (source included) at /afs/cern.ch/exp/ntof/XYMG 2. Detailed description of the routines can be found on as a private Internal Note (accessible to members of the e- group X-Y MicroMegas analysis: how to run the programs, n_TOF-INT , July 2010 New 2D MicroMegas detector for n_TOF beam profile: description and preliminary results, n_TOF-INT , July Now CEA has taken over the work and implemented the suggested improvements namely the integration of the mesh signal in the analysis, which will lead to an improved statistics better calibration especially at higher energies

For the future if needed: proposal for 1 st collimator 23 September 2010M. Calviani - n_TOF Analysis Meeting CERN15 Needs for the 1 st collimator: 1.Understand if tilting is present (it may affect significantly the fluence) 2.Consider the possibility to shift it down into the proper location 2.Shifting Action complex by the fact that it requires lifting an heavy piece The downstream part is fixed into the wall The upstream part can be moved down removal of the filter station adjustment of the TOF line We can measure it with the help of a planar laser, similarly to what we did for the 2 nd collimator it requires some work and still an uncertainty of 1-2 mm is to be taken into account 1.Tilting Filter station 1 st collimator upstream downstream NB: geometer’s independent action

Conclusions 23 September 2010M. Calviani - n_TOF Analysis Meeting CERN16 1.n_TOF beam line up to the Experimental Area is aligned by looking at the spallation target neutron window 2 nd collimator is aligned accordingly 1 st collimator is shifted/tilted, no easy way to move it back to proper position  its effect on the flux reduction account to few % 2.Review of the XYMG analysis as performed in 2009 and beginning of Status of the analysis routines 4. Good agreement with simulated beam profile 1.Indications on the misalignment of the 2 nd collimator 2.Predictions have been verified experimentally  could be used for alignment purposes

23 September 2010M. Calviani - n_TOF Analysis Meeting CERN17 End

23 September 2010M. Calviani - n_TOF Analysis Meeting CERN18 Evident misalignment of the 2 nd collimator upstream bellow ~ 1 cm (?) Upstream bellow Dowstream bellow Upstream bellow Results after the optimizations April 2009 November 2009  also April 2010

23 September 2010M. Calviani - n_TOF Analysis Meeting CERN19 Only 96 strips are read over a total of 106 (effect on beam position)