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Your search keyword '"van der Werf, D. P."' showing total 38 results
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38 results on '"van der Werf, D. P."'

1. Precision spectroscopy of the hyperfine components of the 1S–2S transition in antihydrogen

Author

Baker, C. J., Bertsche, W., Capra, A., Carruth, C., Cesar, C. L., Charlton, M., Christensen, A., Collister, R., Cridland Mathad, A., Eriksson, S., Evans, A., Evetts, N., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Grandemange, P., Granum, P., Hangst, J. S., Hardy, W. N., Hayden, M. E., Hodgkinson, D., Hunter, E., Isaac, C. A., Johnson, M. A., Jones, J. M., Jones, S. A., Jonsell, S., Khramov, A., Kurchaninov, L., Madsen, N., Maxwell, D., McKenna, J. T. K., Menary, S., Momose, T., Mullan, P. S., Munich, J. J., Olchanski, K., Olin, A., Peszka, J., Powell, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sacramento, R. L., Sameed, M., Sarid, E., Silveira, D. M., So, C., Stutter, G., Tharp, T. D., Thompson, R. I., van der Werf, D. P., Wurtele, J. S., and Shore, G. M.

Published
2025
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2. Production of antihydrogen atoms by 6 keV antiprotons through a positronium cloud

Author

Adrich, P., Blumer, P., Caratsch, G., Chung, M., Cladé, P., Comini, P., Crivelli, P., Dalkarov, O., Debu, P., Douillet, A., Drapier, D., Froelich, P., Garroum, N., Guellati-Khelifa, S., Guyomard, J., Hervieux, P-A., Hilico, L., Indelicato, P., Jonsell, S., Karr, J-P., Kim, B., Kim, S., Kim, E-S., Ko, Y. J., Kosinski, T., Kuroda, N., Latacz, B. M., Lee, B., Lee, H., Lee, J., Lim, E., Liszkay, L., Lunney, D., Manfredi, G., Mansoulié, B., Matusiak, M., Nesvizhevsky, V., Nez, F., Niang, S., Ohayon, B., Park, K., Paul, N., Pérez, P., Regenfus, C., Reynaud, S., Roumegou, C., Roussé, J-Y., Sacquin, Y., Sadowski, G., Sarkisyan, J., Sato, M., Schmidt-Kaler, F., Staszczak, M., Szymczyk, K., Tanaka, T. A., Tuchming, B., Vallage, B., Voronin, A., van der Werf, D. P., Won, D., Wronka, S., Yamazaki, Y., Yoo, K-H., and Yzombard, P.

Subjects
High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract

We report on the first production of an antihydrogen beam by charge exchange of 6.1 keV antiprotons with a cloud of positronium in the GBAR experiment at CERN. The antiproton beam was delivered by the AD/ELENA facility. The positronium target was produced from a positron beam itself obtained from an electron linear accelerator. We observe an excess over background indicating antihydrogen production with a significance of 3-4 standard deviations.

Published
2023
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3. Laser cooling of antihydrogen atoms

Author

Baker, C. J., Bertsche, W., Capra, A., Carruth, C., Cesar, C. L., Charlton, M., Christensen, A., Collister, R., Mathad, A. Cridland, Eriksson, S., Evans, A., Evetts, N., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Grandemange, P., Granum, P., Hangst, J. S., Hardy, W. N., Hayden, M. E., Hodgkinson, D., Hunter, E., Isaac, C. A., Johnson, M. A., Jones, J. M., Jones, S. A., Jonsell, S., Khramov, A., Knapp, P., Kurchaninov, L., Madsen, N., Maxwell, D., McKenna, J. T. K., Menary, S., Michan, J. M., Momose, T., Mullan, P. S., Munich, J. J., Olchanski, K., Olin, A., Peszka, J., Powell, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sacramento, R. L., Sameed, M., Sarid, E., Silveira, D. M., Starko, D. M., So, C., Stutter, G., Tharp, T. D., Thibeault, A., Thompson, R. I., van der Werf, D. P., and Wurtele, J. S.

Published
2021
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4. Sympathetic cooling of positrons to cryogenic temperatures for antihydrogen production

Author

Baker, C. J., Bertsche, W., Capra, A., Cesar, C. L., Charlton, M., Mathad, A. Cridland, Eriksson, S., Evans, A., Evetts, N., Fabbri, S., Fajans, J., Friesen, T., Fujiwara, M. C., Grandemange, P., Granum, P., Hangst, J. S., Hayden, M. E., Hodgkinson, D., Isaac, C. A., Johnson, M. A., Jones, J. M., Jones, S. A., Jonsell, S., Kurchaninov, L., Madsen, N., Maxwell, D., McKenna, J. T. K., Menary, S., Momose, T., Mullan, P., Olchanski, K., Olin, A., Peszka, J., Powell, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sacramento, R. L., Sameed, M., Sarid, E., Silveira, D. M., Stutter, G., So, C., Tharp, T. D., Thompson, R. I., van der Werf, D. P., and Wurtele, J. S.

Published
2021
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5. Observation of the 1S–2P Lyman-α transition in antihydrogen

Author

Ahmadi, M., Alves, B. X. R., Baker, C. J., Bertsche, W., Capra, A., Carruth, C., Cesar, C. L., Charlton, M., Cohen, S., Collister, R., Eriksson, S., Evans, A., Evetts, N., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Hangst, J. S., Hardy, W. N., Hayden, M. E., Hunter, E. D., Isaac, C. A., Johnson, M. A., Jones, J. M., Jones, S. A., Jonsell, S., Khramov, A., Knapp, P., Kurchaninov, L., Madsen, N., Maxwell, D., McKenna, J. T. K., Menary, S., Michan, J. M., Momose, T., Munich, J. J., Olchanski, K., Olin, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sacramento, R. L., Sameed, M., Sarid, E., Silveira, D. M., Starko, D. M., Stutter, G., So, C., Tharp, T. D., Thompson, R. I., van der Werf, D. P., and Wurtele, J. S.

Published
2018
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6. Characterization of the 1S–2S transition in antihydrogen

Author

Ahmadi, M., Alves, B. X. R., Baker, C. J., Bertsche, W., Capra, A., Carruth, C., Cesar, C. L., Charlton, M., Cohen, S., Collister, R., Eriksson, S., Evans, A., Evetts, N., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Hangst, J. S., Hardy, W. N., Hayden, M. E., Isaac, C. A., Johnson, M. A., Jones, J. M., Jones, S. A., Jonsell, S., Khramov, A., Knapp, P., Kurchaninov, L., Madsen, N., Maxwell, D., McKenna, J. T. K., Menary, S., Momose, T., Munich, J. J., Olchanski, K., Olin, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sacramento, R. L., Sameed, M., Sarid, E., Silveira, D. M., Stutter, G., So, C., Tharp, T. D., Thompson, R. I., van der Werf, D. P., and Wurtele, J. S.

Published
2018
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7. Limit on the electric charge of antihydrogen

Author

Capra, A., Amole, C., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Butler, E., Cesar, C. L., Charlton, M., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayden, M. E., Isaac, C. A., Jonsell, S., Kurchaninov, L., Little, A., K. McKenna, J. T., Menary, S., Napoli, S. C., Nolan, P., Olchanski, K., Olin, A., Povilus, A., Pusa, P., Robicheaux, F., Sarid, E., Silveira, D. M., So, C., Tharp, T. D., Thompson, R. I., van der Werf, D. P., Vendeiro, Z., Wurtele, J. S., Zhmoginov, A. I., and Charman, A. E.

Published
2017
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8. Antiproton cloud compression in the ALPHA apparatus at CERN

Author

Gutierrez, A., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Burrows, C., Butler, E., Capra, A., Cesar, C. L., Charlton, M., Dunlop, R., Eriksson, S., Evetts, N., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Hangst, J. S., Hardy, W. N., Hayden, M. E., Isaac, C. A., Jonsell, S., Kurchaninov, L., Little, A., Madsen, N., K. McKenna, J. T., Menary, S., Napoli, S. C., Nolan, P., Olchanski, K., Olin, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sacramento, R. L., Sarid, E., Silveira, D. M., So, C., Stracka, S., Tarlton, J., Tharp, T. D., Thompson, R. I., Tooley, P., Turner, M., van der Werf, D. P., Wurtele, J. S., and Zhmoginov, A. I.

Published
2015
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9. The GBAR antimatter gravity experiment

Author

Pérez, P., Banerjee, D., Biraben, F., Brook-Roberge, D., Charlton, M., Cladé, P., Comini, P., Crivelli, P., Dalkarov, O., Debu, P., Douillet, A., Dufour, G., Dupré, P., Eriksson, S., Froelich, P., Grandemange, P., Guellati, S., Guérout, R., Heinrich, J. M., Hervieux, P.-A., Hilico, L., Husson, A., Indelicato, P., Jonsell, S., Karr, J.-P., Khabarova, K., Kolachevsky, N., Kuroda, N., Lambrecht, A., Leite, A. M. M., Liszkay, L., Lunney, D., Madsen, N., Manfredi, G., Mansoulié, B., Matsuda, Y., Mohri, A., Mortensen, T., Nagashima, Y., Nesvizhevsky, V., Nez, F., Regenfus, C., Rey, J.-M., Reymond, J.-M., Reynaud, S., Rubbia, A., Sacquin, Y., Schmidt-Kaler, F., Sillitoe, N., Staszczak, M., Szabo-Foster, C. I., Torii, H., Vallage, B., Valdes, M., Van der Werf, D. P., Voronin, A., Walz, J., Wolf, S., Wronka, S., and Yamazaki, Y.

Published
2015
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10. Observation of the 1S–2S transition in trapped antihydrogen

Author

Ahmadi, M., Alves, B. X. R., Baker, C. J., Bertsche, W., Butler, E., Capra, A., Carruth, C., Cesar, C. L., Charlton, M., Cohen, S., Collister, R., Eriksson, S., Evans, A., Evetts, N., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayden, M. E., Isaac, C. A., Ishida, A., Johnson, M. A., Jones, S. A., Jonsell, S., Kurchaninov, L., Madsen, N., Mathers, M., Maxwell, D., McKenna, J. T. K., Menary, S., Michan, J. M., Momose, T., Munich, J. J., Nolan, P., Olchanski, K., Olin, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sacramento, R. L., Sameed, M., Sarid, E., Silveira, D. M., Stracka, S., Stutter, G., So, C., Tharp, T. D., Thompson, J. E., Thompson, R. I., van der Werf, D. P., and Wurtele, J. S.

Published
2017
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11. An improved limit on the charge of antihydrogen from stochastic acceleration

Author

Ahmadi, M., Baquero-Ruiz, M., Bertsche, W., Butler, E., Capra, A., Carruth, C., Cesar, C. L., Charlton, M., Charman, A. E., Eriksson, S., Evans, L. T., Evetts, N., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayden, M. E., Isaac, C. A., Ishida, A., Jones, S. A., Jonsell, S., Kurchaninov, L., Madsen, N., Maxwell, D., McKenna, J. T. K., Menary, S., Michan, J. M., Momose, T., Munich, J. J., Nolan, P., Olchanski, K., Olin, A., Povilus, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sacramento, R. L., Sameed, M., Sarid, E., Silveira, D. M., So, C., Tharp, T. D., Thompson, R. I., van der Werf, D. P., Wurtele, J. S., and Zhmoginov, A. I.

Published
2016
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12. Microwave-plasma interactions studied via mode diagnostics in ALPHA

Author

Friesen, T., Andresen, G. B., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Bowe, P. D., Butler, E., Cesar, C. L., Chapman, S., Charlton, M., Eriksson, S., Fajans, J., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayano, R. S., Hayden, M. E., Humphries, A. J., Hydomako, R., Jonsell, S., Kurchaninov, L., Madsen, N., Menary, S., Nolan, P., Olchanski, K., Olin, A., Povilus, A., Pusa, P., Robicheaux, F., Sarid, E., Silveira, D. M., So, C., Storey, J. W., Thompson, R. I., van der Werf, D. P., Wurtele, J. S., Yamazaki, Y., and ALPHA Collaboration

Published
2012
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13. Trapped antihydrogen

Author

Butler, E., Andresen, G. B., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Bowe, P. D., Cesar, C. L., Chapman, S., Charlton, M., Deller, A., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayden, M. E., Humphries, A. J., Hydomako, R., Jenkins, M. J., Jonsell, S., Jørgensen, L. V., Kemp, S. L., Kurchaninov, L., Madsen, N., Menary, S., Nolan, P., Olchanski, K., Olin, A., Povilus, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sarid, E., Seif el Nasr, S., Silveira, D. M., So, C., Storey, J. W., Thompson, R. I., van der Werf, D. P., Wurtele, J. S., Yamazaki, Y., and ALPHA Collaboration

Published
2012
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14. Alternative method for reconstruction of antihydrogen annihilation vertices

Author

Amole, C., Ashkezari, M. D., Andresen, G. B., Baquero-Ruiz, M., Bertsche, W., Bowe, P. D., Butler, E., Cesar, C. L., Chapman, S., Charlton, M., Deller, A., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayano, R. S., Hayden, M. E., Humphries, A. J., Hydomako, R., Jonsell, S., Kurchaninov, L., Madsen, N., Menary, S., Nolan, P., Olchanski, K., Olin, A., Povilus, A., Pusa, P., Robicheaux, F., Sarid, E., Silveira, D. M., So, C., Storey, J. W., Thompson, R. I., van der Werf, D. P., Wurtele, J. S., Yamazaki, Y., and ALPHA Collaboration

Published
2012
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15. Further evidence for low-energy protonium production in vacuum

Author

Lodi Rizzini, E., Venturelli, L., Zurlo, N., Charlton, M., Amsler, C., Bonomi, G., Canali, C., Carraro, C., Fontana, A., Genova, P., Hayano, R., Jørgensen, L. V., Kellerbauer, A., Lagomarsino, V., Landua, R., Macrí, M., Manuzio, G., Montagna, P., Regenfus, C., Rotondi, A., Testera, G., Variola, A., and van der Werf, D. P.

Published
2012
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17. Towards antihydrogen trapping and spectroscopy at ALPHA

Author

Butler, E., Andresen, G. B., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Bowe, P. D., Bray, C. C., Cesar, C. L., Chapman, S., Charlton, M., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Hangst, J. S., Hardy, W. N., Hayano, R. S., Hayden, M. E., Humphries, A. J., Hydomako, R., Jonsell, S., Kurchaninov, L., Lambo, R., Madsen, N., Menary, S., Nolan, P., Olchanski, K., Olin, A., Povilus, A., Pusa, P., Robicheaux, F., Sarid, E., Silveira, D. M., So, C., Storey, J. W., Thompson, R. I., van der Werf, D. P., Wilding, D., Wurtele, J. S., Yamazaki, Y., and ALPHA Collaboration

Published
2011
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18. Towards antihydrogen confinement with the ALPHA antihydrogen trap

Author

Fujiwara, M. C., Andresen, G., Bertsche, W., Boston, A., Bowe, P. D., Cesar, C. L., Chapman, S., Charlton, M., Chartier, M., Deutsch, A., Fajans, J., Funakoshi, R., Gill, D. R., Gomberoff, K., Hangst, J. S., Hardy, W. N., Hayano, R. S., Hydomako, R., Jenkins, M. J., Jørgensen, L. V., Kurchaninov, L., Madsen, N., Nolan, P., Olchanski, K., Olin, A., Page, R. D., Povilus, A., Robicheaux, F., Sarid, E., Silveira, D. M., Storey, J. W., Thompson, R. I., van der Werf, D. P., Wurtele, J. S., and Yamazaki, Y.

Published
2006
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19. Production of slow protonium in vacuum

Author

Zurlo, N., Amoretti, M., Amsler, C., Bonomi, G., Carraro, C., Cesar, C. L., Charlton, M., Doser, M., Fontana, A., Funakoshi, R., Genova, P., Hayano, R. S., Jørgensen, L. V., Kellerbauer, A., Lagomarsino, V., Landua, R., Lodi Rizzini, E., Macrì, M., Madsen, N., Manuzio, G., Mitchard, D., Montagna, P., Posada, L. G., Pruys, H., Regenfus, C., Rotondi, A., Testera, G., Van der Werf, D. P., Variola, A., Venturelli, L., and Yamazaki, Y.

Published
2006
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20. Production and detection of cold antihydrogen atoms

Author

Amoretti, M., Amsler, C., Bonomi, G., Bouchta, A., Bowe, P., Carraro, C., Cesar, C. L., Charlton, M., Collier, M. J. T., Doser, M., Filippini, V., Fine, K. S., Fontana, A., Fujiwara, M. C., Funakoshi, R., Genova, P., Hangst, J. S., Hayano, R. S., Holzscheiter, M. H., Jørgensen, L. V., Lagomarsino, V., Landua, R., Lindelöf, D., Rizzini, E. Lodi, Macrì, M., Madsen, N., Manuzio, G., Marchesotti, M., Montagna, P., Pruys, H., Regenfus, C., Riedler, P., Rochet, J., Rotondi, A., Rouleau, G., Testera, G., Variola, A., Watson, T. L., and van der Werf, D. P.

Published
2002
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21. Producing Slow Antihydrogen for a Test of CPT Symmetry with ATHENA

Author

Fujiwara, M. C., Amoretti, M., Amsler, C., Bendiscioli, G., Bonomi, G., Bouchta, A., Bowe, P., Carraro, C., Charlton, M., Collier, M., Doser, M., Filippini, V., Fine, K., Fontana, A., Funakoshi, R., Genova, P., Grögler, D., Hangst, J. S., Hayano, R. S., Higaki, H., Holzscheiter, M. H., Joffrain, W., Jorgensen, L., Lagomarsino, V., Landua, R., Lenz Cesar, C., Lindelöf, D., Lodi-Rizzini, E., Macri, M., Madsen, N., Manuzio, G., Marchesotti, M., Montagna, P., Pruys, H., Regenfus, C., Riedler, P., Rotondi, A., Rouleau, G., Salvini, P., Testera, G., van der Werf, D. P., Variola, A., Venturelli, L., Watson, T., Yamazaki, T., and Yamazaki, Y.

Published
2001
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22. Trapped antihydrogen

Author

Andresen, G. B., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Bowe, P. D., Butler, E., Cesar, C. L., Chapman, S., Charlton, M., Deller, A., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayden, M. E., Humphries, A. J., Hydomako, R., Jenkins, M. J., Jonsell, S., Jørgensen, L. V., Kurchaninov, L., Madsen, N., Menary, S., Nolan, P., Olchanski, K., Olin, A., Povilus, A., Pusa, P., Robicheaux, F., Sarid, E., Nasr, S. Seif el, Silveira, D. M., So, C., Storey, J. W., Thompson, R. I., van der Werf, D. P., Wurtele, J. S., and Yamazaki, Y.

Published
2010
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27. Investigation of buffer gas trapping of positrons.

Author

Baker, C J, Isaac, C A, Edwards, D, Evans, H T, Clayton, R, van der Werf, D P, and Charlton, M

Subjects
POSITRONS, ELECTRONIC excitation, ENERGY dissipation, GASES, POSITRONIUM
Abstract

A study of positron capture in a two-(pressure) stage buffer gas accumulation apparatus is presented for a variety of species, including some molecules which are known to be either efficient for positron trapping, or are frequently used to cool the particles when held in these devices. Absolute accumulation efficiencies are reported for all species. A detailed optimisation procedure, which has identified the main processes responsible for positron capture and loss in the trap, has been deployed to explore accumulation efficiency as the gas pressure and the electrostatic well depth in the trap are systematically varied. Accumulation exploiting energy loss via molecular vibrational transitions has been observed for the first time for a number of gases, though at much lower efficiency than achieved using electronic excitation processes. [ABSTRACT FROM AUTHOR]

Published
2020
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30. Positron annihilation in small molecules.

Author

Charlton, M., Giles, T., Lewis, H., and van der Werf, D. P.

Subjects
POSITRON annihilation, GASES, CHEMICAL kinetics, GAS dynamics, HYDROGEN
Abstract

Positron annihilation in room temperature samples of the molecular gases N2, O2, CO, N2O and CH4 has been studied in the density range below 10 amagat using the positron lifetime technique. Careful analyses of the density dependence of the free positron annihilation rates have been performed that have allowed the annihilation parameter, ‹Zeff›, to be extracted. We compare our results to those in the literature, and give recommended ‹Zeff› values from experiment. We have also synthesized the existing data for H2 and derived a recommended value for the annihilation parameter for this molecule. [ABSTRACT FROM AUTHOR]

Published
2013
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31. The behaviour of positron clouds in the single-particle regime under the influence of rotating wall electric fields.

Author

Van der Werf, D. P., Isaac, C. A., Baker, C. J., Mortensen, T., Kerrigan, S. J., and Charlton, M.

Subjects
*POSITRONS, *ELECTRIC fields, *ANNIHILATION reactions, *PHYSICS, *GASES
Abstract

Positron clouds are compressed following accumulation in a Surkotype two-stage buffer gas trap using an asymmetric rotating wall electric field. An analytic theory used to describe measurements of the rate of compression is discussed. Furthermore, we describe measurements taken without the rotating wall applied and with the rotating wall compression present during accumulation of the positron cloud. This has enabled total loss rates for the positrons via annihilation and collisional-induced radial transport to be isolated, with the latter mechanism found to be dominant. We have shown that the application of the rotating wall at a resonant frequency virtually eliminates radial transport, such that the positron loss is caused by annihilation in the gas. [ABSTRACT FROM AUTHOR]

Published
2012
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32. Antihydrogen for precision tests in physics.

Author

Charlton, M., Jonsell, S., Jørgensen, L. V., Madsen, N., and van der Werf, D. P.

Subjects
ATOMS, ANTIMATTER, PROPERTIES of matter, MAGNETIC fields, FIELD theory (Physics), PHYSICAL & theoretical chemistry
Abstract

The creation of atoms of antihydrogen under controlled conditions has opened up a new era in physics with antimatter. We describe the experimental realisation of low energy antihydrogen, via the mixing of carefully prepared clouds of positrons and antiprotons, and some of the progress that has been made in the last few years in characterising properties of the nascent anti-atoms. Ongoing efforts aimed at trapping the anti-atoms in magnetic field minima are discussed. Some of the motivations for undertaking experiments with antihydrogen are presented. [ABSTRACT FROM AUTHOR]

Published
2008
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33. Design and operation of a two-stage positron accumulator.

Author

Clarke, J., van der Werf, D. P., Griffiths, B., Beddows, D. C. S., Charlton, M., Telle, H. H., and Watkeys, P. R.

Subjects
*POSITRON beams, *GAS dynamics, *COOLING, *NITROGEN, *SCIENTIFIC apparatus & instruments
Abstract

A compact positron accumulator based upon a simple two-stage buffer gas cooling scheme is described. Its operation to produce 10–20 ns wide bursts containing around 105 positrons with cycling times in the 100 ms to 1 s range is discussed. Departures of the behavior of the accumulator from that expected of such an instrument are presented. The utility of these effects in diagnosing accumulator performance is described. [ABSTRACT FROM AUTHOR]

Published
2006
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34. Development and applications of time-bunched and velocity-selected positron beams.

Author

Merrison, J. P., Charlton, M., Aggerholm, P., Knudsen, H., van der Werf, D. P., Clarke, J., and Poulsen, M. R.

Subjects
POSITRON beams, CAPACITORS, COMPUTER simulation, RADIOACTIVITY, ENERGY storage
Abstract

We describe the development of an instrument for the production of low energy positron beams that are bunched in time, and the use of a velocity selection device. The bunching unit was constructed from forty seven separate elements, coupled in series in a capacitor chain to reduce the delay time for propagation of the applied voltage pulse along the electrode system and to facilitate operation at frequencies up to 100 kHz. A parabolic potential distribution for time focusing was used. Tests with a dc positron beam produced from a radioactive source are described, together with measurements in which the buncher was used to compress positron pulses produced from an electron accelerator-based beam. Computer simulations of particle trajectories in the buncher have been performed resulting in a detailed evaluation of the factors that govern and limit the time resolution of the instrument. A sector magnet used to velocity-select intermediate energy positrons is described and its performance discussed. [ABSTRACT FROM AUTHOR]

Published
2003
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35. Positron annihilation study of the diffusion of oxygen in annealed silicon-doped gallium arsenide.

Author

Towner, A. C., Nathwani, M., Saleh, A. S., van der Werf, D. P., and Rice-Evans, P.

Subjects
POSITRON annihilation, DIFFUSION, GALLIUM arsenide
Abstract

Positron annihilation spectroscopy has been applied to silicon-doped GaAs grown by molecular-beam epitaxy. Annealing SiO[sub 2] capped samples at 930°C causes the SiGa - VGa vacancies to become positively charged. The SiO[sub 2] caps cause oxygen to diffuse beneath the surface and the spectroscopy leads to the first measurement of the oxygen diffusion coefficient in GaAs. The application of a new analysis program ROYPROF reveals the creation of internal electric fields. [ABSTRACT FROM AUTHOR]

Published
2002
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36. Manipulation of the magnetron orbit of a positron cloud in a Penning trap.

Author

Mortensen, T., Deller, A., Isaac, C. A., van der Werf, D. P., Charlton, M., and Machacek, J. R.

Subjects
MAGNETRONS, ORBITS (Astronomy), PENNING traps, PARTICLE size distribution, STABILITY theory, ELECTRIC potential, ELECTRODES
Abstract

We describe a simple and versatile method to manipulate the amplitude of the magnetron orbit of ions stored in a Penning trap, applied here to a cloud of low energy positrons. By applying a pulsed voltage to a split electrode in the trap, which is normally used for rotating wall compression of the particles, the size of the magnetron orbit can be changed at will. The modified orbit has been shown to be stable for many magnetron periods. The technique could find use in applications which require off-axis ejection of particles, for instance in the filling of arrays of traps for multicell positron storage. [ABSTRACT FROM AUTHOR]

Published
2013
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37. Antimatter transport processes.

Author

Van Der Werf, D. P., Andresen, G. B., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Bowe, P. D., Bray, C. C., Butler, E., Cesar, C. L., Chapman, S., Charlton, M., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Hangst, J. S., Hardy, W. N., Hayano, R. S., Hayden, M. E., and Humphries, A. J.

Published
2010
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