To do for the next K0 beam time

1. To do for the next K0 beam time Department of Physics,Tohoku University H. Kanda

2. “Next” what? • The next beam times in September • Preparation status of the LD2 target and a vacuum gamma beam duct • The coming beam time already proposed and approved • Neutron detector for NKS2 • Beam profile monitor • The experimental plan to be proposed in the near future • Investigation of “quasi-freedom” of deuteron target LNS Nuclear Physics Working Group

3. Preparation of the LD2 target • We have modified our LD2 target • elongation of the insertion part to fit the dimension of the 680 magnet • new TMP port for speeding up the vacuum pumping • Direct attachment of the TMP greatly worked to shorten the pumping periodOld cryostat: Roughly 1 night to pump down to 1x10-5 mbar for starting the refrigeratorNew cryostat: Only 1 hour to pump! LNS Nuclear Physics Working Group

4. Preparation of the LD2 target • Elongation should have changed the thermal condition inside the cryostat which will force modification of the liquefaction and vapor-suppressing method. • Vapor-suppression is essential to reduce the ambiguity of the target density. However, vapor suppressed state is identified only by a phase diagram. • We have to re-build the vapor-suppression method for the new cryostat and see the liquid without any vapor bubbles by our eyes. And the test of the long term (~ one week) stability is prefered. • These test should be finished until mid-September for the installation and the stable operation in the next next beam time. Operation point Time course of the temperatures and phase diagram measured by the old cryostat. LNS Nuclear Physics Working Group

5. What’s the trouble? • The liquid deuterium is consisted of ICF34 flange, an aluminum shell (EB-welded), the polyimide film (adhered on the aluminum shell), and a flange for the liquid temperature monitor (sealed by an indium wire). • Gas leak happened when the cell is refrigerated down to 150 ~ 200 K. • REFINED: adhering method of polyimide film, tightening of ICF flange, tightening of indium seal • LEAK TESTED (in LN2): an ICF flange, film surfaces, and adhered surfaces • TESTED but NOT ISOLATED: indium seal and flange for the thermometer (thermometer is adhered through the hole of the flange) • The flange for the thermometer is now the most suspicious for the source of the leakage. The isolation of the seal and the flange itself is quit difficult... Blank flange is needed to be relieved that the seal is good. LNS Nuclear Physics Working Group

6. Preparation of the vacuum gamma beam duct • Gamma beam travels through the air as long as 3.2 m (1.1x10-2 X0) after the collimator to the target. • A vacuum duct of 2 m long (4.4x10-3 X0 including film-windows: 50mm, and the remaining air) reduced the trigger rate by 30 % with STag=2MHz and 2mm thick acrylic target. • A vacuum duct of 3 m long (9.9x10-4 X0) is now planned to replace the old one. Thinner film (25mm) will be used. The new one is estimated to reduce the trigger rate by 45 %. Pirani gauge Pair magnet ~3.0m Plan view of the pair magnet, the 680 magnet, and some elements for gamma beam line. gamma beam pump LNS Nuclear Physics Working Group

7. Neutron detector • Multi-pion photoproduction experiment: LNS Exp#2551 was approved last year to run with the K0 photoproduction experiment: #2552. In the proposal, I commented to place the neutron detector at the forward of the NKS2.... No preparation is carried out so far. • However, the neighbor of the NKS2 is too crowded now to place the large object as the neutron detector (a passage will be lost). LNS Nuclear Physics Working Group

8. Beam profile monitor • The only solution to make room for the neutron detector is to remove the HSBPM by Ishikawa-san and Koutaku-san, which played the important role in the beam tuning period. • X-ray imaging camera “Remote RadEye” might be one of the good replacements of the HSBPM and Polaroid films. Thanks to its small size, it will be easy to place it on the Lead glass counter. LNS Nuclear Physics Working Group

9. Investigation of “quasi-freedom” of the deuteron target • In our result of pion photoproduction on proton and deuteron, interesting phenomena could be seen. • The double pion photoproduction cross sections on free proton are consistent with the results from other experiments. • The cross sections on quasi-free proton, namely proton in deuteron, are smaller than the results from other experiments. They resemble to the double pion photoproduction cross sections on quasi-free neutron. • The single pion photoproduction cross sections are in good agreement with the other results. • Can deuteron be considered as the quasi-free target of nucleon? Which is the most likely view, in these words as quasi-, semi-, pseudo-, non-, and anti-? • Detailed analysis for final states will reveal more precise view of the “quasi-freedom” of the deuteron. (needs hermetic detector system and more statistics) LNS Nuclear Physics Working Group

10. Cross sections for gp -> pp+p- and gp -> D++p- LNS Nuclear Physics Working Group

11. Cross sections for g”p” -> pp+p- compared with other results for “p” target and “n” target LNS Nuclear Physics Working Group

12. Cross sections for gd -> ppp- LNS Nuclear Physics Working Group

13. Summary • I’m sorry for the delay of the preparation of the liquid deuterium target. • I’m sorry for the delay of the preparation of a neutron detector. • Pion photoproduction experiment showed an interesting results. Detailed investigation will provide us of more interesting results. LNS Nuclear Physics Working Group