You will be presented with the full text of a science research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
the atlas detector@xcite , one of the two general - purpose experiments at the large hadron collider ( lhc ) at cern , has been taking proton - proton collision data at a centre - of - mass energy of 7  tev since march 2010 . the atlas inner detector ( id)@xcite combines silicon detector technology ( pixels@xcite and microstrips@xcite ) in the innermost part with a straw drift detector@xcite with transition radiation detection capabilities ( transition radiation tracker , trt ) on the outside , operating in a 2-t superconducting solenoid .    the microstrip detector ( semiconductor tracker , sct ) , as shown in fig .
[ fig : id ] , forms the middle layer of the i d between the pixel detector and the trt .
the sct system comprises a barrel@xcite made of four nested cylinders and two end - caps@xcite of nine disks each .
the barrel layers carry 2112  detector units ( modules)@xcite altogether , while a total of 1976  end - cap modules@xcite are mounted on the disks .
the whole sct occupies a cylinder of 5.6  m in length and 56  cm in radius with the innermost layer at a radius of 27  cm .
the silicon modules@xcite consist of one or two pairs of single - sided p-_in_-n microstrip sensors glued back - to - back at a 40-mrad stereo angle to provide two - dimensional track reconstruction .
the @xmath0-@xmath1 thick sensors@xcite have 768 ac - coupled strips with an @xmath2 pitch for the barrel and a pitch for the end - cap modules .
barrel modules follow one common design , while for the forward ones four different types exist according to their position in the detector .
the readout@xcite of each module is based on 12  abcd3ta asics@xcite manufactured in the radiation - hard dmill process mounted on a copper / kapton hybrid .
each module is designed , constructed and tested to operate as a stand - alone unit , mechanically , electrically , optically and thermally .
the performance of the sct modules and substructures have been repeatedly tested in the past in dedicated beam tests ( before 2004 ) , during the combined test beam with other i d components in summer 2004 and with cosmic rays@xcite both on the surface and after installation in the atlas cavern . since autumn
2009 various aspects of the sct operation have been studied continuously while recording physics data in @xmath3 collisions at 900  gev , 2.36  tev and , since march 2010 , at 7  tev .
the sct performs very well with increasing collision rate , as demonstrated in fig .
[ fig : error1 ] , where the fraction of sct module sides giving errors as a function of time is shown .
it is stressed that the time interval spans an increasing instantaneous luminosity of five orders of magnitude .
the sct data - quality inefficiency is mainly due to hv ramping up during lhc stable - beam declaration , with an overall 99.9% operation efficiency .
the total fraction of data with sct errors remained less than 0.25% throughout 2010 .
the only issues encountered affecting the  otherwise stable  sct configuration are : ( a ) a faulty connection to a cooling loop@xcite discovered during commissioning , that can not be repaired since it is located behind the endplate ; and ( b ) some unexpected failures@xcite of off - detector optical transmitters ( tx - plugins)@xcite that are being replaced by humidity - resistant plugins . in total , more than 99% of all sct modules are fully operational .
noise measurements are performed by two methods:@xcite injection of calibration pulses and noise estimation from response - curve fit ; and measuring noise occupancy as a function of threshold to extract the input noise .
the measured values are well correlated and , as shown in fig .
[ fig : no - strips ] ( left ) , the noise occupancy is well below the required level of @xmath4 .
good agreement has been observed between monte carlo and 900  gev data in the number of hits per module side , as shown in fig .
[ fig : no - strips ] ( right ) .
the discrepancy at low @xmath5 is due to the lower noise assumed in simulation compared to data by approximately a factor of three .
as far as the sct timing@xcite is concerned , per - module adjustments are made to account for the optical fibre length and the time - of - flight from the interaction point though timing scans .
the related measurements show that the sct is well synchronized with the level-1 trigger .
the lorentz angle as determined by finding the angle corresponding to the minimum cluster width is shown in fig .
[ fig : lorenz - eff ] ( left ) for the barrel layers and for various data / conditions .
the measurements agree well with the predictions , proving the good signal digitization in the full simulation .
the intrinsic strip efficiency is computed by counting missed hits in well - reconstructed tracks with @xmath6 , excluding dead modules and chips .
the sct hit efficiency for all three sct parts ( shown in fig .
[ fig : lorenz - eff ] , right , for the end - cap c ) is well above the 99% specification .
the radiation damage is being monitored through the leakage current .
the comparison between measurements and fluka@xcite predictions of the fluence shows good agreement in the barrel region , whilst a discrepancy in the low-@xmath7 forward region is under study .
the leakage current evolution with time lies within @xmath8 of the predicted values .
the long - term monitoring of the effect during operation continues .
the atlas semiconductor tracker performance shows excellent performance .
a total of 99.1% of the sct modules are used for data taking . noise occupancy and hit efficiency are well within the design specifications .
the optical transmitter failures are understood and do not impair data taking efficiency .
the monte carlo simulation reproduces accurately the detector geometry and material budget .
the radiation damage is being monitored and is in good agreement with expectations .
the sct is a key precision tracking device in atlas and we are taking more and more good physics data every day .
the sct commissioning and running experience is used to extract valuable lessons for future silicon strip detector projects .
the author acknowledges support by the spanish ministry of science and innovation ( micinn ) under the project fpa2009 - 13234-c04 - 01 , by the ramn y cajal contract ryc-2007 - 00631 of micinn and csic , and by the spanish agency of international cooperation for development under the pci project a/030322/10 .
the semiconductor tracker ( sct ) is a silicon strip detector and one of the key precision tracking devices in the inner detector of the atlas experiment at cern lhc . 
 the completed sct has been installed inside the atlas experimental cavern since 2007 and has been operational since then . 
 calibration data has been taken regularly and analyzed to determine the performance of the system . in this paper the current status of the sct 
 is reviewed , including results from data - taking periods in 2010 and 2011 . 
 we report on the operation of the detector including overviews on services , connectivity and observed problems . 
 the main emphasis is given to the performance of the sct with the lhc in collision mode and to the performance of individual electronic components .