Yu Tsyganov 08 Sept NEC 2009 Varna Bulgaria

Yu. Tsyganov 08 Sept. NEC’ 2009 Varna, Bulgaria Statistical model of PIPS detector operating in a real-time mode. Yu. S. Tsyganov FLNR, JINR Content 1) Introduction Synthesis of SHE at the Dubna Gas-filled Recoil, PIPS detector, EVR-α(n)-SF correlations…technical systems. . etc. 2) Active correlations technique – radical suppression of beam associated backgrounds a) Idea; b) Algorithm for PIPS position sensitive detector, realization ; c) Statistical analysis of the candidate to event measured with the mentioned method 3) Summary Target wheel mounting

The Dubna Gas –Filled recoil Separator (JINR+LLNL since ~2001) Radioactive target design ( six sectors), Foil – 1. 5 mcm Ti. GSI, RIKEN *. . . * Experiment 226 Ra+48 Ca 270 Hs+4 n DGFRS, 2008

DGFRS + Detection module

DGFRS+ Backgrounds (a few words) • Maim advantage of Gas Field separators – transport efficiency • Everything else : drawbacks. eg. Separation high cyclotron vacuum and working volume of the separator, separation working area of the separator and TOF module (vacuum or pentane. . ), is not easy to provide linear measurement of the beam dose (cross section? ), high intensity beam stop is near 2 -3 m with respect to detection module etc. . etc) (!) especially : there are backgrounds in the beam On phase imitating well α-decays, that is, creating no signal in TOF module DETECTION in real-time mode a candidate to ER –α chain is suppress radically such a background and provide a minimum loss in the whole efficiency (units of prc -10%) Main histogram – spectrum with suppression both TOF and VETO detector. Right hand tail is evident. Whereas, right-upper corner histogram is with real-time detection of ER-alpha chains

Real-time algorithm ( in brief. In details – my report at NEC-2007 +Nucl. Inst. &Meth. A 513(2003), A 558(2006), A 525(2004), A 573(2007), A 477(2002), J. Phys. G. 25(1999)937) last versions: PSD-7 conf. (Liverpool, UK(2005)sept. , & 6 th Balkan Phys. Union Conf. , Istanbul (2006) sept. ) idea: Yu. S. Tsyganov (NEC’ 97 (Sept. , VARNA, Bulgaria) +HPC’ASIA-97, Seoul Hilton, Seoul, rep. Korea (May, 1997) static Real PIPS detector (12 strip) dynamic Image in PC Case of EVR – alpha, // in the case of ER-alpha || alpha-alpha both matrixes are static If there will follow an event under interest in the beam Off pause in the same strip , it will be pause prolongation up to 10 -30 min automatically

Plus one explanation schematics * Flowchart of the process *B. N. Gikal: private communication Principle of background suppression

Statistical significance of the event (main part) • One of the key questions of a rare event detecting procedure is a probability of the candidate to the real event to be a random • • In principle there are two basic approaches: LDSC (K. -H. Schmidt et al. , Z. Phys. A 316 (1984)19 and BSC (V. B. Zlokazov , Yad. Fiz. V. 66, № 9 (2003)1714). . others. . Can be easily represent according to the basis these concepts LDSC – formalize the concept of a Linked Decay Signal Combination sequence analyzed does fit in this concept or not. ( in brief: a-priori info “Yes”) // key term – link between signals or between “starter” signal and following on the scenario BSC – ) signal, depending formalize the concept of Background Signal Combination and test, whether the signal sequence analyzed does fit the concept or not (a-priori info “No”) // key term – time interval between “start” and “finish”

LDSC, BSC (mnemonics) K-H. Schmidt, LDSC V. B. Zlokazov, BSC

K. -H. Schmidt mnemonics (graphs) EVR Fixed Order EVR Partially free Order a(i) SF time EVR time SF Flexible order (Yu. Tsyganov, JINR comm. P 7 -2008 -189) In the manner, similar to K. -H. Schmidt : Alpha-decays Or, in simplified form: Spontaneous SF Fission time T – effective time T=npixels. T (exp), M signals are attributed to “unknown” nuclides and N-M-2 – to “known”. N- total number, including one SF. N SF-total fission fragment Number, λ-appropriate rates of event per coordinate pixel.

Active correlation method (EVR-α break points) • Graph for this case will be as shown in the figure: Small dead time ~102 μs

LDSC philosophy frame for active correlation method (approach similar to BSC is in my paper Phys. Of Part. & Nucl. Lett. Vol. 6 (2009) 59 -62 ) • Being considering in the described above process a definite order correlated pair recoil-alpha E 1 E 2 as a starter signal Ê1 (E 1 E 2) forthcoming sequences of “ ” -decays and following to the philosophy of [6] one can rewrite the equation (1) for the given case in the form of: • Here the parameter denotes not any single signal rate per pixel, but a rate of correlations/pauses generating by the detection system during a long term experiment. Therefore, if NSTOP is a total number of pauses measured in an experiment, to a first approximation : • Simplifications (only alpha decays, &λi Δti << 1) a mean counting rate value for alpha – decay signals measured in beam-OFF pauses by the focal plane detector. More common case of “starter” correlation signal Note, that Nstop is a value measured in experiment!!!

Practical examples from SHE experiments… • “advantage factor” (def) ξ = nb( KHS )/nb( present report), • That is : (see also Yu. Tsyganov JINR P 13 -2008 -92, p. 6) Example #1 , Z=113 from the reaction 273 Np+48 Ca 282113+3 n; [Yu. Oganessian et al. PRC v. 76 (2007)011601® ]. t 1=0 (EVR), t 2=0. 0889 s, t 3=0. 0951 s, t 4= 0. 568 s, t 5= 88. 548, t 6=1993 s (SF). ξ=9532. 68/523. 655 ≈ factor of 20 and nb ≤ 5∙ 10 -14 Example#2 Z=118 from the reaction 249 Cf+48 Ca 294118+3 n; t 1 = 0 (EVR), t 2=0. 000456, t 3=0. 001467, t 4 = 0. 012864 SF). ξ≈ 2 (except of ~10 -12 in the original paper) [ Yu. Oganessian et al. PRC v. 74(2006)p. 044602].

Supplement #1 (math. vs phys. , general phylosophy // in the form of hyposthesis) Idealization nb << 1 Real case f (nb / p. CONFIG)=ńb ńb << 1 The simplest way ~ nb/pconf

examples • Example #1 EVR – α – SF short chains (N=6 , geom. Eff. For α – about 85%, second nuclide branch to SF ~ • • 50%. Combination Nα=0 (real SHE experiments) ). One event has nb~0. 3. Having considering combination probability P(6, 0) – zero non-completed chains from six attempts, t. i. For our case p= 0. 5*0. 85=0. 425, x( number of full event)=0, n=6. ńb=0. 3/0. 036 >>1 ! and this event should be excluded from the list Example #2 Registration of one multi chain event like EVR-α-α-α-SF (see. Yu. Oganessian et al. , Revista Mexicana de Fisica 46 Suplemento 1 (2000)35 ) All three alpha are with y-position and have full energy. Probability of this fact is p ~ (0. 67) 3≈0. 3. P(1, 1) = p 1∙(1 -p)0=0. 3 ( additionally, one can take into account that efficiency to detect both fragments is not 100%, but around 40% !) V. B. Zlokazov Yad. Phys. V. 66 N 9 (2003) 1718. Nm~0. 0004 (one pixel) => nb~200 Nm=0. 08 So, ńb ~0. 08/0. 3 ≈0. 3 (large enough!) => It’s difficult to say anything definite!!! (event or not event =to be or not to be!)

Yu. S. Tsyganov. NEC’ 2009 Sept. 08, Varna In memory of S. Iliev One of the best electronics engineer in the field of super heavy elements research SUMMARY (only two conclusions can be drawn here) 1) Modification of LDSC method to estimate statistical significance of the multi-chain event measured with a position sensitive PIPS detector has been performed for the method of “active correlations” (case EVR-alpha ) 2) As a reasonable scenario, it is proposed to use some additional knowledge about event property (a priori +a posteriori. . etc) to compare any calculated (LDSC or BSC…) statistic parameter with the real probability of the measured configuration of the candidate // in the form of hypothesis