Next Generation Cavity and Coupler Interlock for the European XFEL

The safe operation of cavities and couplers in the European XFEL accelerator environment is secured by a new technical interlock (TIL) design, which is based on the XFEL crate standard (MTCA™.4). The new interlock is located inside the accelerator tunnel. Several remote testcapabilities ensure the correct operation of sensors for light, temperature and free electrons. Due to the space costs and the very high number of channels, the electronic concept was moved from a conservative, mostly analog electronic approach, with real comparators and thresholds, to a concept, where the digitizing of the signals is done at a very early stage. Filters, thresholds and comparators are moved into the digital part. The usage of an Field Programmable Gate Array (FPGA) and an additional watchdog (WD) increase the flexibility dramatically, with respect to be as reliable as possible. An overview of the system is shown

Development of a new B-Mapping System for SRF Cavity Vertical Tests

Magnetic flux trapped in the Niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity of the surface resistance to trapped magnetic flux is mainly determined by the pre-treatment, the cavity geometry and the Niobium grain size and orientation. To potentially improve the flux expulsion characteristics and hence the efficiency of future accelerator facilities further studies of the trapping behavior are essential. For this purpose a so-called "B-Mapping System" to monitor the magnetic flux along the outer cavity surface of SRF 1.3 GHz TESLA-Type single-cell cavities is currently under development at DESY. Contrary to former approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs

Development of a new B-Mapping System for SRF Cavity Vertical Tests

Magnetic flux trapped in the Niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity of the cavity to trapped magnetic flux is mainly determined by the treatment, the geometry and the Niobium grain size and orientation. To potentially improve the flux expulsion characteristics of SRF cavities and hence the efficiency of future accelerator facilities, further studies of the trapping behavior are essential. For this purpose a so-called B-mapping system to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities is currently under development at DESY. Contrary to former approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs. Furthermore, the signal-to-noise ratio (SNR) and consequently the measuring sensitivity can be enhanced by shorter analog signal lines, less thermal noise and the Mu-metal shielding of the cryostat. In this contribution the design, the development process as well as first performance test results of the B-mapping system are presented

Development of a New B-Mapping System for SRF Cavity Vertical Tests

Magnetic flux trapped in the Niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity of the surface resistance to trapped magnetic flux is mainly determined by the pre-treatment, the cavity geometry and the Niobium grain size and orientation. To potentially improve the flux expulsion characteristics and hence the efficiency of future accelerator facilities further studies of the trapping behavior are essential. For this purpose a so-called "B-Mapping System" to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities is currently under development at DESY. Contrary to former approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs

European XFEL Linac RF System Conditioning and Operating Test

96 accelerating modules with 768 TESLA / European XFEL type superconducting cavities were installed in the European XFEL LINAC tunnel (XTL) in fall 2016. Warm conditioning of the RF system - High/Low Level RF System and main input couplers - begun even before finishing the accelerator installation works. All modules were conditioned and tested prior to the installation in the tunnel in the AMTF test stand at DESY. Nevertheless, due to some repair activities on warm Input coupler parts, warm conditioning was needed on a few modules/couplers. Cooling down to 2K begun in December 2016 and was finished in January 2017. Since then cold conditioning and tests are running. A few Input couplers did have problems with conditioning and were disconnected, limiting otherwise the system performance. Some cavities in the modules showed multipacting (MP) effects, mostly because the cavity vacuum was vented with dry nitrogen gas because of mentioned repairs on couplers in some modules. Such MP effects did appear in AMTF as well. All MP effects were successfully conditioned until now

Feasibility of CW and LP Operation of the XFEL Linac

The Eu­ro­pean XFEL su­per­con­duct­ing linac is based on cav­i­ties and cry­omod­ules (CM) de­vel­oped for TESLA lin­ear col­lider. The XFEL linac will op­er­ate nom­i­nally in short pulse (sp) mode with 1.3 ms RF pulses (650 μs rise time and 650 μs long bunch train). For 240 ns bunch spac­ing and 10 Hz RF-pulse rep­e­ti­tion rate, up to 27000 bunches per sec­ond can be ac­cel­er­ated to 17.5 GeV to gen­er­ate uniquely high av­er­age bril­liance pho­ton beams at very short wave­lengths. While many ex­per­i­ments can take ad­van­tage of full bunch trains, oth­ers pre­fer an in­creased to sev­eral μ-sec­onds in­tra-pulse dis­tance be­tween bunches, or short bursts with a kHz rep­e­ti­tion rate. For these types of ex­per­i­ments, the high av­er­age bril­liance can be pre­served only with duty fac­tors much larger than that of the cur­rently pro­posed sp op­er­a­tion. In this con­tri­bu­tion, we dis­cuss progress in the R&D pro­gram for fu­ture up­grade of the Eu­ro­pean XFEL linac, namely an op­er­a­tion in the con­tin­u­ous wave (cw) and long pulse (lp) mode, which will allow for more flex­i­bil­ity in the elec­tron and pho­ton beam time struc­ture

SRF Gun Cavity R&D at DESY

SRF Gun Cavity is an ongoing accelerator R&D Project at DESY, being developed since several years. Currently several SRF gun cavity prototypes were simulated, built and tested in our Lab and elsewhere. Lately the 1.6 cells niobium cavity with Pb thin film cathode was tested in a vertical cryostat with a different cathode plug configurations. Cathode plug design was improved, as well as SRF gun cavity cleaning procedures. Results ofthe last cavity performance tests are presented

Horizontal RF Test of a Fully Equipped 3.9 GHz Cavity for the European XFEL in the DESY AMTF

In order to validate the cavity package concept before the module preparation for the European XFEL Injector, one 3.9 GHz cavity, complete with magnetic shielding, power coupler and frequency tuner was tested in a specially designed single cavity cryomodule in one of the caves of the DESY Accelerator Module Test Facility (AMTF). The cavity was tested in high power pulsed operation up to the quench limit of 24 MV/m, above the vertical test qualifications and all subsystems under test (coupler, tuner, waveguide tuners, LLRF system) were qualified to design performances

Frequent and sex-biased deletion of SLX4IP by illegitimate V(D)J-mediated recombination in childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) accounts for ∼25% of pediatric malignancies. Of interest, the incidence of ALL is observed ∼20% higher in males relative to females. The mechanism behind the phenomenon of sex-specific differences is presently not understood. Employing genome-wide genetic aberration screening in 19 ALL samples, one of the most recurrent lesions identified was monoallelic deletion of the 5' region of SLX4IP. We characterized this deletion by conventional molecular genetic techniques and analyzed its interrelationships with biological and clinical characteristics using specimens and data from 993 pediatric patients enrolled into trial AIEOP-BFM ALL 2000. Deletion of SLX4IP was detected in ∼30% of patients. Breakpoints within SLX4IP were defined to recurrent positions and revealed junctions with typical characteristics of illegitimate V(D)J-mediated recombination. In initial and validation analyses, SLX4IP deletions were significantly associated with male gender and ETV6/RUNX1-rearranged ALL (both overall P < 0.0001). For mechanistic validation, a second recurrent deletion affecting TAL1 and caused by the same molecular mechanism was analyzed in 1149 T-cell ALL patients. Validating a differential role by sex of illegitimate V(D)J-mediated recombination at the TAL1 locus, 128 out of 1149 T-cell ALL samples bore a deletion and males were significantly more often affected (P = 0.002). The repeatedly detected association of SLX4IP deletion with male sex and the extension of the sex bias to deletion of the TAL1 locus suggest that differential illegitimate V(D)J-mediated recombination events at specific loci may contribute to the consistent observation of higher incidence rates of childhood ALL in boys compared with girls