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in the future linear collider detectors the forward region is instrumented with two low angle electromagnetic calorimeters , denoted hereafter as * lumical * and * beamcal*. the luminosity calorimeter ( * lumical * ) precisely counts the number of bhabha events and enables the measurement of the luminosity spectrum using the acollinearity angle of bhabha scattering@xcite .
the beam calorimeter ( * beamcal * ) extends the angular coverage of the forward calorimeters down to polar angles of about 10 mrad .
both calorimeters are centered around the axis of the outgoing beams and consist of 3.5 mm - thick tungsten plates , each corresponding to about one radiation length , interspersed with segmented sensor layers .
all detectors in the very forward region have to tackle relatively high occupancy , requiring dedicated front - end electronics . the forward region layout foreseen for the ild detector
is shown in figure  [ fig : forward_structure ] .
prototype detector planes assembled with dedicated fe and adc asics for * lumical * and for * beamcal * have been built . in this paper , results of the * lumical * performance following tests in a mixed particle and in an electron beam are reported .
during 2014 and 2015 , the * fcal * collaboration has successfully commissioned and operated , in the t9 experimental area at the cern ps facilities and in the 21 beam line area at the desy ii synchrotron , the first * lumical * multi - layer prototype . a multi - plane module with four sensor planes
was investigated in a mixed particle and in an electron beam .
different detector configurations were used during the testbeams , with the active sensor layers always separated by one or two absorber layers .
the testbeam was performed in october 2014 at the cern ps facilities using a secondary beam with muons , pions , hadrons and electrons with momentum of 5gev / c .
the beam momentum can be fixed by the magnetic field of the beam delivery electromagnets while the horizontal spatial spread is reduced by a set of collimators .
the simplified overall ( without magnets ) of the ps facilities is presented in figure  [ fig : ps_line ] .        in order to enable the particle track reconstruction , a multilayer tracking detector , so - called telescope ,
was developed by the aarhus university .
the telescope utilizes the mimosa26 chips , a maps with fast binary readout @xcite .
the mimosa26 utilizes a binary readout indicating the pixel signals exceeding the preset discrimination level .
the pixel matrix is read continuously ( without triggering ) providing a complete frame every 115.2  @xmath0s .
the data are gathered , triggered and stored by a custom daq system , based on the pxi crate , developed by the aarhus university in collaboration with strasbourg university .
four telescope planes , each comprising one mimosa26 chip , were set upstream of the * dut * as shown in figure  [ fig : cern_set - up ] .
the trigger system consists of three scintillators with compact photomultipliers .
two solid 5@xmath15mm@xmath2 scintillators were placed upstream and downstream the telescope and one , with a 9  mm diameter circular hole , was placed just before the last telescope plane .
the * dut * ( lumical detector prototype ) , was prepared using four detector planes always separated by two absorber layers as shown in figure  [ fig : dut_cern ] .
the complex mechanical structure developed by cern allows to install the tungsten absorber or active sensor layer with a precision of a few tens of micrometers .
a fully assembled detector plane is shown in figure  [ fig : pcb_old ] @xcite .
the prototype system consists of a silicon sensor covered by kapton fanout and front - end electronics
.    21  cm@xmath2.,scaledwidth=35.0% ]    due to high energy depositions in the * lumical * calorimeter , standard 320  @xmath0 m thick silicon sensors were chosen as a compromise between the capacitance and the amount of generated charge . *
lumical * sensors have been designed at the institute of nuclear physics pan in cracow @xcite and manufactured by hamamatsu photonics .
the sensor is made from a n - type silicon , with p@xmath4pads with a thin aluminum metalization .
the sensor tile , as the smallest sensor unit produced , includes 256 separate sensor pads .
for this experiment 32 channels readout module was used .      during october 2015
, four detectors were installed on the tungsten layers and installed inside the same frame as we used during the 2014 test beam as shown in figure  [ fig : desy_dut ] .
the whole system was installed in 5 gev electron beam at desy .
the beam line was composed of scintillators for the trigger and six planes of silicon used as a telescope @xcite as shown in figure  [ fig : desy_exp_set_up ] .
a crucial point in the measurements was the synchronization between the data acquired with the detectors under investigation and that of the tracker .
the latter was used to measure the local detection efficiency and evaluate the level of cross - talk between neighboring pads as function of the particle impact location .
this was effectively achieved employing the rd51 scalable readout system ( srs ) .
the data acquisition of both systems ( silicon tracker and lumical detector ) was triggered by the same scintillator signals and performed with a single srs front - end card ( fec ) @xcite .
for each triggered event , the charge accumulated by all channels was stored . for each channel
, the charge was sampled in 25 bins of 25 ns each .
the mmdaq1 online data acquisition software was used to store the synchronized data on a pc for further analysis . using the online , it is possible to visualize events . on the figure  [ fig : adc_256 ]
, we can see a typical event : the adc counts ( pedestal subtracted ) as a function of the channel number ( between 1 and 256 ) and the time ( between 0 and 500 ns ) .
the aim of the test beam was to fully equipped four silicon sensors and installed these sensors in between two tungsten planes , namely within one mm .
we modified the read out kapton foil including two 130 pin connectors ( figure  [ fig : ch_fanout ] ) so we will be able to read all the pads of a sensors .
the high voltage was originally injected from on the 3.5 mm pcb but to cope with the one mm , we designed a thin high voltage kapton foil as shown in the figure  [ fig : hv_fanout ] .            in order to mechanically support the sensor and the two kapton foils , we designed an envelope , which should also fit within 1 mm .
we used two different techniques to produce the envelope : 3d printing and carbon fiber .
it appears that the 3d printed envelop is not rigid enough so we finally choose the carbon fiber option , which allows thickness of  200  @xmath0 m and a good rigidity .
the whole detector ( see figure  [ fig : desy_sensor ] including the carbon fiber , the two kapton foils and the sensor ) thickness was measured in different positions around 900  @xmath0 m .
an important effort has been realized on the gluing layers thickness and on the wire bonding loop size : some tools have been developed in order to be able to apply glue layers of 20 to 30  @xmath0 m .
we developed an expertise to maintain the wire bonding loop size around 50  @xmath0 m .    in order to read all the pads of each sensor ( 128 channels ) we used the apv25 chip .
one hybrid contains 128 channels , which each are ac coupled to one read - out strip of the detector .
each channel contains a pre - amplifier , cr - rc shaper with adjustable shaping time and has a spark protection system implemented .
the hybrid records the value of the shaped signal every 25 ns and stores it in an analog memory consisting of a 192 celled pipe - line .
the signal is read out upon a trigger signal .
the number of samples in one acquisition window is user defined , and the trigger time delay must hence be adjusted by the user to synchronize the trigger with the acquisition window .
the apv hybrids are connected to the adapter boards using commercial hdmi cables .
one cable can serve two apv hybrids ( a master and a slave card ) that can be connected through a 16-lead flat cable .
the hybrid cards are connected to the detector ground through two low - ohmic low - profile rf coaxial connectors , which also serve to fix the hybrid card mechanically .
the testbeam campaigns were done to investigate the performance of the calorimeter prototype .
data were taken for different pads and also for regions covering pad boundaries .
the impact point on the sensor is reconstructed from the telescope information . using a color code for the signals on the pads
the structure of the sensor becomes nicely visible , as seen in figure  [ fig : impact_points ] .        during the test beam ,
the response of the readout chain to electromagnetic shower was studied . in order to analyze the electromagnetic shower development
the energy deposited in each sensor plane from all configuration were obtained .
the shower can be therefore sampled up to the 10@xmath5 layer with the target spatial sampling resolution of one radiation length , by combining the data obtained in all three configurations .
the measurement results from october 2014 test beam were compared with prediction of geant4 monte carlo simulations where the experimental setup was implemented .
a good agreement was found between them as shown in figure  [ fig : long_shower ] .
data taken in tests beam were processed using various algorithms to investigate the response of large - area pad sensors assembled with a full readout chain .
a first * lumical * multi - layer silicon - sensor prototype was tested at the ps cern facilities with a mixed - particle beam and at the desy ii synchrotron with a 5 gev electron beam .
the mc simulation of the testbeam was performed with a fair level of detail and the experimental data are in good agreement with mc simulations .
the obtained results indicate an excellent working performance of all components ( silicon sensors , front - end and readout electronics ) and fulfilled the requirements for * lumical * calorimeter . using new technology and expertise and each construction step , we succeeded to develop , produce and test detector less than 1 mm thick modules ( 900  @xmath0 m ) .
the first results of a four layers fully equipped have started and results are promising .
this work was partially supported by the romania uefiscdi agency under pn - ii - pt - pcca-2013 - 4 - 0967 project , the israel science foundation ( isf ) , the german - israel foundation ( gif ) and i - core .
100            j. blocki et al . , _ silicon sensors prototype for the lumical
_ , eudet - memo-2009 - 07 , ( 2009 ) , http://www.eudet.org/e26/e28/e42441 . s. martoiu , h. muller ; j. toledo , _ front - end electronics for the scalable readout system of rd51 _ , nuclear science symposium and medical imaging conference ( nss / mic ) * ieee * ( 2011 ) .
the * fcal * collaboration is preparing large scale prototypes of special calorimeters to be used in the very forward region at a future linear electron positron collider for a precise and fast luminosity measurement and beam - tuning . 
 these calorimeters are designed as sensor - tungsten calorimeters with very thin sensor planes to keep the moliere radius small and dedicated fe electronics to match the timing and dynamic range requirements . 
 a partially instrumented prototype was investigated in the cern ps t9 beam in 2014 and at the desy - ii synchrotron in 2015 . 
 it was operated in a mixed particle beam ( electrons , muons and hadrons ) of 5 gev from ps facilities and with secondary electrons of 5 gev energy from desy - ii . 
 the results demonstrated a very good performance of the full readout chain . 
 the high statistics data were used to study the response to different particles , perform sensor alignment and measure the longitudinal shower development in the sandwich . 
 in addition , geant4 mc simulations were done , and compared to the data .    
 calorimeters , front - end electronics for detector readout